There are two types of proxies:
General - gives authority to someone to represent the owner and cast a vote on their behalf based on how the representative desires.
Directed - gives authority to someone to represent the owner and cast a vote on their behalf based on how the owner directs them to vote.
Proxies typically must be returned by the start of the meeting.
A ballot should be filled out for each proxy (as only ballots are counted).
An absentee vote is a ballot filled out and turned in or mailed to the board. Typically, these are only authorized if statutes or governing documents allow. When the governing documents do not allow absentee voting, many Associations simply use directed proxies (as it's the next closet thing but your vote will not be secret).
This article may be better at explaining it:
Directed Proxies vs. Absentee Ballots: What is the Difference and Can Our Association Use Them? from an attorney in Wisconsin. Statutes differ between States and you should check your applicable statutes to verify any advice in article is applicable to your Association.