- Digital brain
- A living knowledge graph built from your real work — transcripts, documents, conversations, and frameworks — that AI agents can reason with, not just search. Where a notes archive stores what you know, a digital brain connects it and answers questions grounded in your own data. It is the term BrainGraph uses for the step beyond a second brain.See how BrainGraph builds your digital brain →
- Second brain
- The popular term, from the Personal Knowledge Management world, for an external system that stores what you know — usually notes in a tool like Obsidian or Notion. A second brain stores; a digital brain connects and reasons. BrainGraph builds what people often call a second brain, then takes it further into a digital brain an AI can actually act on.From a second brain to your own digital brain system →
- Knowledge graph
- A way of storing information as entities — people, projects, topics — connected by relationships, often pictured as dots and lines. Unlike a folder of documents, a knowledge graph lets you see how everything links and ask questions across all of it at once. It is the structure underneath a digital brain.BrainGraph →
- Graph database
- The type of database a knowledge graph runs on. It stores not just data but the connections between data — which is what lets a digital brain answer questions a normal document store or spreadsheet cannot. It shows how information is linked, not just what the information is.
- Node
- A single point in a knowledge graph — a person, an organization, a project, a topic, or a concept. Nodes are the things your digital brain knows about; edges are how they connect.
- Edge
- A relationship between two nodes in a knowledge graph — for example, "this meeting discussed pricing" or "this client uses that framework." Edges are what turn a pile of separate facts into a graph you can reason across.
- Entity
- A real thing your digital brain knows about — a person, company, project, or concept — with a single canonical record. Matching every mention in your documents back to the right entity is what keeps the graph clean and trustworthy.
- Fact
- A single statement in your digital brain that connects two entities — the atomic unit of knowledge. Facts carry their source, so you can always trace where a piece of knowledge came from.
- Knowledge base
- A store of what you or your business knows. A knowledge base is a database; a digital brain is a knowledge base structured as a graph, so an AI can reason across it instead of only retrieving from it.
- AI agent
- A piece of software that can think and act within your knowledge space — prepare a meeting, score a lead, draft a message — using your digital brain as its source of truth. An agent decides nothing on its own authority; it surfaces and drafts, and you keep the judgment.Connect agents to your brain via the Claude connector →
- Agent orchestration
- Coordinating multiple AI agents so they work together on top of one digital brain — each handling a part of a larger workflow, all reasoning from the same shared knowledge.
- Skill file
- A markdown file — often with a .skill extension — that gives an AI agent step-by-step instructions for one specific task or workflow. The AI reads it and follows it; a good skill file behaves like a small, dedicated brain for a narrow job.
- Soul file
- A file that defines an AI agent's behavior and character — how it responds. Give an agent a "strict" soul file and its output comes back strict. Where a memory file is what the agent knows, a soul file is how it says it.
- Memory file
- A file that holds an AI agent's knowledge — the short, core layer of what it knows. Deeper knowledge lives in separate files; the memory file is the concise reference the agent reads to give grounded answers. Paired with a soul file, it is what makes an agent's responses both informed and in-character.
- MCP (Model Context Protocol)
- An open standard that lets an AI tool — Claude, ChatGPT, and others — securely connect to an outside source, like your digital brain, and use it during a conversation. BrainGraph ships an MCP connector so you can query your brain and save notes straight from chat.The BrainGraph MCP connector →
- RAG (Retrieval-Augmented Generation)
- A technique where an AI retrieves relevant information from an outside source before it answers, instead of relying only on its training. A digital brain is that source — and a graph-based digital brain retrieves connected context, not just matching snippets, so the answer reflects how your knowledge actually fits together.
- Personal Knowledge Management (PKM)
- The practice of capturing, organizing, and reusing what you learn. PKM is the discipline behind the "second brain" — and a digital brain is PKM taken one step further: organized so an AI can act on it, not just so you can find it later.
- Ingestion
- The process of turning your raw material — transcripts, emails, documents, article URLs, videos — into a structured knowledge graph. Ingestion is the step that makes a digital brain out of a pile of files.
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