A wiki is a website designed for collaborative editing, letting many people create, update, and organize content directly in a web browser.

They emphasize simplicity and openness — pages can be created or modified without special technical skills, and most maintain an edit history so revisions can be reviewed or reverted.

Key features
- **Collaborative editing:** Multiple people can edit the same pages, occasionally concurrently.
- **Edit history:** Each change is logged with a time and the editor’s name or IP.
- **Interlinking:** It’s easy to create links between pages, forming an interconnected knowledge base.
- **Lightweight markup:** Simple markup languages (such as WikiText or Markdown) are used to format pages.
- **Permission settings:** Wikis may allow public editing or restrict changes to registered or authorized users.
- **Discussion pages:** Talk or discussion pages let contributors debate edits and organization.

Typical uses
- Crowd-sourced knowledge resources (e.g., Wikipedia)
- Project documentation and internal company knowledge repositories
- Cooperative writing and shared notes
- Educational and classroom projects

Pros
- **Fast collaboration:** Multiple people can add and refine content quickly.
- **Openness:** Edit histories and talk pages reveal how content decisions were made.
- **Expandable:** Wikis can grow naturally as contributors add new topics.

Drawbacks
- **Vandalism and false information:** Open editing may allow intentional or accidental inaccuracies.
- **Inconsistent quality:** Articles can differ greatly in depth, tone, and reliability.
- **Organizational issues:** Without clear governance, content may become fragmented or disputed.

Illustration
- **Wikipedia** — the best-known wiki, run by the Wikimedia Foundation and built by volunteer contributors worldwide.