The best way to get to know all Bones-characters is of course, by starting at the beginning of the series. If you start watching in the midst of season 3 you will have missed out on a lot of what makes Bones such an incredibly great show.
If you still insist on getting to know the characters in another way, Wikipedia is your safest bet:
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On the Wikipedia page you will see a column (right under the introduction) that reads 'contents'.
You will find that in getting to know the show, it's easiest to start by reading '2.1 Plot Summary' followed by '3 Characters'.
You can click on names of various characters to go to their character biography page.
You might also like to try FOX's official BONES site. You'll find it under the following link:
link
Again; I recommend you start watching season 1 first :)
Have fun!