Bulbapedia is an encyclopedia about Pokémon to which anyone can contribute. Since its launch in February 2005, it has grown to include 28,019 articles on a range of Pokémon-related topics.
This hub page is designed to help editors find something to work on. It covers a range of ways you can share your Pokémon knowledge with the world including creating wanted pages, expanding stub articles, and cleaning up poorly written pages. It also lists specific short-term tasks that need to be finished. Some of the work might be tedious, but a little goes a long way in building an encyclopedia.
If you have any questions, feel free to ask on the talk page. Alternatively, you could ask a specific staff member. They're happy to help you out.