Concept	Claude	ChatGPT	Gemini
Reusable assistant Something repeatable. Think instructions, context, and rules that you can invoke in multiple sessions to produce consistent results.	Skill A packaged assistant with custom instructions and uploaded resources (optional), reusable across chats.	Custom GPT A packaged assistant with custom instructions and uploaded resources (optional), reusable across chats.	Gem A packaged assistant with custom instructions and uploaded resources (optional), reusable across chats.
Agents Agents perform multi-step tasks. This is what most of us think of when we think “AI.” You give it an instruction, and the agent goes and works its magic, returning a result.	Workflow / Cowork Cowork (a desktop tool for non-developers) or Claude Code (for developers and the nerds among us). Claude Desktop does similar stuff. Drives tasks across files, connectors, and code.	Agent Mode Fires on a task-by-task basis from the composer. Plans and executes using a virtual browser, code execution, and connectors.	No single named feature The closest thing to “agents” is a combination of Deep Research and Canvas. You tie them together.
Persistent workspace A set of instructions, files, and a chat history the model can use to carry out a specific type of task without re-explanation.	Project A workspace with custom instructions, uploaded files, and its own separate chat history. Context stays within the project.	Project A workspace with custom instructions, uploaded files, and its own separate chat history. Context stays within the project.	Gem + Drive, or NotebookLM Gemini doesn’t have “Projects” per se. They have a combination of Gems, Drive access, and NotebookLM. Don’t let the multiple tools scare you. It’s very, very powerful.
Custom instructions The “system prompt” we’ve all heard so much about. They apply to every chat, no matter what.	User preferences / Styles Global instructions about you and how to respond. Applies to every chat unless overridden inside a Skill or Project.	Custom instructions Global instructions about you and how to respond. Applies to every chat unless overridden inside a Custom GPT or Project.	Saved info Global instructions about you and how to respond. Applies to every chat unless overridden inside a Gem.
App and service connectors How you connect to other services like Google Drive. Doesn’t include MCP servers or custom API connections.	Connectors First-party connections to external apps.	Connectors / Apps First-party connections to external apps.	Workspace integration / Extensions It’s Google, so native integration with Gmail, Docs, Sheets, Drive, Calendar, and Meet built in. Otherwise, first-party connectors to external apps.
Command-line agents Direct, non-GUI access to the AI. It’s a great nerd flex, and it’s the most powerful way to access the model.	Claude Code Command-line tool that drives the model from the terminal. Also has IDE integration with VS Code and other tools.	Codex CLI Command-line tool that drives the model from the terminal.	Gemini Code Assist / Gemini CLI Command-line tool that drives the model from the terminal. Also has IDE integration with VS Code and other tools.
Project context file (for command-line agents) A markdown file placed in your project root or in the directory tree. The CLI agent reads it before performing a task. This is the CLI agent’s superpower. Learn to use it!	CLAUDE.md A markdown file the agent loads before it executes any task within that directory tree. Note that Claude will accept AGENTS.md as well.	AGENTS.md A markdown file the agent loads before it executes any task within that directory tree.	GEMINI.md A markdown file the agent loads before it executes any task within that directory tree.