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:** Numerous contributors can work on pages, sometimes simultaneously.
- **Edit history:** Each change is logged with a time and the editor’s name or IP.
- **Interlinking:** Creating links among pages is straightforward, which helps interconnect content.
- **Lightweight markup:** Simple markup languages (such as WikiText or Markdown) are used to format pages.
- **Permission settings:** Some wikis are open to anyone; others limit edits to registered users or specific groups.
- **Discussion pages:** Talk or discussion pages let contributors debate edits and organization.

Frequent uses
- Crowd-sourced knowledge resources (e.g., Wikipedia)
- Internal documentation and company knowledge bases
- Collaborative writing and shared note-taking
- Classroom and educational projects

Pros
- **Fast collaboration:** Contributors can rapidly create and improve content.
- **Openness:** Transparency through revision histories and discussions.
- **Expandable:** Wikis can grow naturally as contributors add new topics.

Cons
- **Vandalism and false information:** Open contribution can result in deliberate or accidental misinformation.
- **Inconsistent quality:** Entries may vary in accuracy, style, and completeness.
- **Organizational issues:** Poor coordination or governance can cause content fragmentation and disputes.

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