Both por and pro can correspond to English 'for'. However, por indicates for a goal (the more usual sense of English 'for') while pro indicates for a cause and more often may be translated 'because of': To vote por your friend means to cast a ballot with their name on it, whereas to vote pro your friend would mean to vote because of something that happened to them or something they said or did.
Both por and pro can correspond to English 'for'. However por indicates for a goal (the more usual sense of English 'for',) while pro indicates for a cause and more often may be translated 'because of': To vote por your friend means to cast a ballot with their name on it, whereas to vote pro your friend would mean to vote because of something that happened to them or something they said or did.