Wikis are online databases that allow users to add and edit content using a web browser. They enable collaboration and knowledge sharing within organizations. Wikis are used by companies for documentation, building online communities, collaborating with customers, maintaining FAQs and policies. While wikis provide advantages like collaboration and mobility, they also have disadvantages like potential disorganization, need for maintenance, and security issues. Overall, wikis are useful for sharing information but difficult to maintain and information accuracy can be questionable.