What Is Obsidian? And Why People Call It a "Second Brain"

Obsidian is a note-taking app that stores notes as Markdown files on your device. You can link those notes into a personal knowledge system, often called a second brain. The app is free to use, including for work; optional services cover syncing and web publishing.

What is Obsidian?

Obsidian is a notes app — and yes, it shares a name with the volcanic glass, which is why your search results were confusing. The app is what this page is about.

Your notes live in an ordinary folder, and a link such as [[Client name]] connects one note to another. You can open Markdown files in other editors. That portability is useful, though plugins, attachments and special formatting may need additional care when moving a vault.

For example, a client note can link to a meeting, the meeting to a quote and the quote to the procedure used to deliver the work. The links provide paths back to the source rather than relying on memory.

What is a "second brain"?

A second brain is a simple idea: stop trusting your memory with things a system should hold. Write it down once, in one place, linked to what it relates to — so retrieving it takes seconds instead of a search through email, texts, and the truck's glovebox.

Tiago Forte popularized the second-brain approach in Building a Second Brain, including the PARA organization model and CODE process. You can apply a knowledge-management method in different tools. Obsidian is one option when local files and links suit the way you work.

Why do business owners use one?

Consider the questions an owner repeatedly answers: what was agreed with a client, why a policy changed or where the latest procedure lives. Keeping dated, linked notes can make those answers easier to retrieve. It still takes a habit of recording decisions and updating stale material.

A useful starter vault can hold client notes, meeting records, procedures and decisions. Add access controls and backups appropriate to the information. Local storage gives you control over files; it does not replace data protection or retention decisions.

Obsidian vs. Notion vs. Google Docs — which should you use?

Choose by the work: shared structured databases, collaborative documents or a personal linked record. Test the actual export, offline and collaboration behavior your team needs.

Notion supports offline pages in its desktop and mobile apps, with some block and database limitations. Google Docs also supports configured offline work. Obsidian's distinction is that its notes are local Markdown files by default, not that it is the only tool you can use offline or export.

What happens when you connect AI to it?

An approved connector can let an assistant retrieve notes and cite the records it used. That can improve access to business context, but it does not guarantee a correct answer. Restrict the vault scope, review source dates and check whether the cited note supports the conclusion.

The plumbing is a standard connector called an MCP server, and it's less exotic than it sounds. We run this setup daily.

For a setup walkthrough, see the guide to connecting Claude Code with an Obsidian vault. Verify the installed plugin version and enabled connector before granting access, especially when the vault contains client information.

How to start (without organizing your whole life first)

The people who fail at this start by designing the perfect system. The people who succeed start by writing one note. Three steps:

Download Obsidian and create a vault in a folder you control. Start with a small set of notes and configure a separate backup before expanding.

1. Write today's notes there — and nowhere else. The next client call, the next meeting, the next "I should write that down." One place, starting now.
2. Link as you go. When a note mentions a client or a job, type the name in double brackets. That's it. Structure grows out of links; you don't have to design it up front.

Add existing notes when they become useful. Avoid a large migration before you know the retrieval questions you need the system to answer. If you sync devices, use one supported sync strategy and test conflicts and recovery.

Book a 30-minute call to discuss your workflow, ask questions and decide on a useful next step, with no obligation.

Reference: https://obsidian.md/pricing

Reference: https://help.obsidian.md/sync-notes

Reference: https://www.notion.com/help/use-pages-offline

Reference: https://support.google.com/docs/answer/6388102