can anyone please explain how to distinguish between the usage of who and whom. i understand that the difference here is subject vs object pronoun but could someone elaborate a little bit more.

more importantly, can anyone point to a link where i can find all the uncommon pronouns - subject vs object (or pronouns in general). for example, i am familiar with he/she vs him/her, they vs their. but there must be some other uncommon ones like who vs whom.

thanks.