What Are Claude Skills?
No jargon. No assumptions. A plain-language guide with actual files opened up and explained, so you can see exactly what's happening when Claude creates things for you.
Have you ever asked Claude to "create a PowerPoint presentation" or "read this PDF" — and it actually gave you a real downloadable file? That wasn't Claude improvising. Behind the scenes, it opened a set of specialized instructions, followed a procedure, and used real software tools to build that file.
Those instructions are called Skills. And you've been using them without knowing it.
This two-part guide explains everything — in plain language, with zero technical prerequisites. Part 1 (this article) covers what Skills are, shows you the actual files inside them, and explains how they work. Part 2 walks through real-life scenarios step by step.
Think of Claude as a Restaurant
Imagine Claude is a very talented chef. Without Skills, this chef can cook — but they're improvising every dish from memory. Sometimes brilliant. Sometimes inconsistent.
Skills are the recipe books, the specialized tools, and the prep instructions. When you order a specific dish (ask Claude to make a spreadsheet), the kitchen doesn't wing it — it pulls out the exact recipe, grabs the right pans, and follows a proven procedure.
The menu at the front? That's the Skill descriptions — short, one-line summaries. Claude glances at every menu item to figure out which recipe matches your order. The recipe book only gets opened after you order. And the ingredients (specialized code, templates) only get grabbed when the chef is ready to cook.
That's the whole idea. Skills give Claude specialized knowledge for specific tasks. When your request matches a Skill, Claude uses it. When it doesn't, Claude just talks to you normally — which is still very good, but it's the difference between "here are some ideas for slides" and "here's your actual PowerPoint file."
What's Actually Inside a Skill?
This is where most explanations get abstract. Not this one. Let's open up a real Skill and look at every file. Below is an interactive file explorer showing the actual contents of Claude's Word Document Skill — the Skill that activates when you ask Claude to create a .docx file.
Click any file in the sidebar to see what's inside and why it matters:
That's a real Skill. It's just a folder with text files and code scripts. The SKILL.md is the brain — the instructions Claude follows. The scripts are the hands — the tools Claude runs to build actual files. The templates help with advanced operations like tracked changes.
The Three Layers — Every Skill Works This Way
No matter which Skill you look at — PDFs, spreadsheets, presentations — they all follow the same pattern:
The name and description at the top of SKILL.md. Claude reads these for every installed Skill at the start of every conversation. This is how it knows what's available. Takes up very little memory — like a one-line menu entry.
The full instructions in SKILL.md. Only loaded when Claude decides your request matches. This tells Claude how to approach the task — what libraries to use, what formatting standards to follow, what common mistakes to avoid.
The scripts, templates, and reference files in subfolders. Only loaded when the instructions specifically call for them. These are the actual tools Claude runs — Python scripts that validate files, JavaScript code that builds documents, templates for complex formatting.
This is why Skills don't slow Claude down. Most of the time, Claude only carries Layer 1 (the menu). It only loads the heavier layers when you actually need them.
Peeking Inside Other Skills
Let's look at how different Skills are organized. Each one is tailored to its job — some are simple, some are complex, but they all follow the same folder-with-SKILL.md pattern.
The PDF Skill — Two Skills Working Together
PDFs are complex enough that Anthropic split the work into two Skills: one for reading PDFs and one for creating/editing them. Here's what each contains:
The File Reading Skill — The Traffic Cop
This is the most interesting Skill to understand, because it solves a problem most people don't think about: not all files can be opened the same way. If Claude tried to read a PDF the way it reads a text file, it would get garbled nonsense. The File Reading Skill is a routing table — it looks at the file type and tells Claude which tool to use:
The Internal Comms Skill — A Different Shape
Not all Skills create files. The Internal Comms Skill is a writing guide — it teaches Claude how to write company-style updates, newsletters, and FAQs. Instead of scripts, it has example documents that show Claude the expected format:
See the pattern? Every Skill is a folder. Every folder has a SKILL.md. But what's inside varies wildly — scripts for file creation, reference docs for complex tasks, example formats for writing. The Skill is whatever Claude needs to do the job well.
What Happens When You Ask — Step by Step
Now that you've seen what's inside a Skill, let's watch it work. Click each step to expand:
"Create a 10-slide pitch deck for my bakery. Include slides for our story, menu highlights, financials, and next steps."
Claude sees "pitch deck" + "slides" and matches it to the pptx Skill, whose description says: "Trigger whenever the user mentions deck, slides, presentation, or a .pptx filename." This takes a fraction of a second.
Now Claude knows: use PptxGenJS library, follow the layout guide in pptxgenjs.md, validate the file after creation, use thumbnail.py to check the visual output. All from the SKILL.md file we explored above.
Claude has access to a private computer (a virtual machine). It writes and runs real code — not a simulation. The output is a genuine PowerPoint file that opens in any presentation software.
You can preview it right in Claude, download it, open it in PowerPoint or Google Slides, add your own photos, and present it tomorrow. It's a real file you own.
Jargon Buster — Terms You'll See Online
Now that you understand what Skills are, here's a quick reference for the technical terms you'll encounter if you read more about them:
Which Skill Am I Using?
Pick a task. We'll tell you which Skill activates and what files inside it do the work:
One Tip That Changes Everything
"Give me some ideas for a presentation about my bakery"
Result: Text in chat. No file. No Skill activated.
"Create a 10-slide PowerPoint presentation about my bakery"
Result: Downloadable .pptx file. Presentation Skill activated.
The difference is asking for a file instead of text. When you say "PowerPoint," "Word document," "spreadsheet," "PDF" — those words trigger Skills. When you just ask for ideas or text, Claude stays in conversation mode.
Both are useful. But knowing the difference lets you choose which one you want.
You Don't Need to Be Technical
Everything in this article — the SKILL.md files, the scripts, the progressive disclosure — is what's happening behind the scenes. You don't need to understand any of it to benefit. Skills activate automatically. Just ask Claude for what you need. But if you ever wonder "how did Claude do that?" — now you know.