Well, if you have to ask it means you have a lot of research to do, I give you a few pointers:

Here a study published by Larry Sanger, co-founder of Wikipedia:

https://larrysanger.org/2020/05/wikipedia-is-badly-biased/

Last bug not least, Wikipedia have been infiltrated at all levels , not only at ideological level but at corporate level with a massive bias to push for their donors commercial interest, I personally had to deal with that years ago, it was amusing to corroborate personally what many where already exposing.

Yet, a large amount of the population keep looking at Wikipedia as a good source of information...

It is so bad, that when I use AI language models I explicitly request the model to remove Wikipedia as a source of information...