The purpose of votes isn't reputation. The purpose of votes is to determine what the community thinks of a particular post. It happens that on main, posts that are voted on are rewarded/sanctioned by reputation, but this isn't the case on meta. It doesn't mean votes are pointless, because they still fulfill their primary purpose: determining what the ...
The measure is the number of posts, comments, edits, and votes cast over the last 60 days.
This is explained in the hover-text.
The official source also mentions that deleted content is not taken into account and that self-edits do not count.
While it is not put on display one can also sort user on main by this criterion: https://math.stackexchange....
Voting on meta.math.SE does not affect reputation anywhere.
(However, the badges you gain on meta.math.SE are separate from your badges on math.SE.)
Your meta.math.SE reputation is a copy of your math.SE reputation, though sometimes it takes a few hours to update to the latest value. This is how all meta.____.SE sites work, except for meta.stackoverflow.
Reputation here is entirely derived from the main website; your reputation is the same here as it is there, synchronized hourly. Votes here do not affect your reputation in any way. However, you can earn unique badges here on the meta site.
I've learned about this from this answer on meta.SO.
EDIT: It seems that the above link to faq ...
From help center:
Votes on meta do not affect your reputation; your meta reputation is the same as your reputation on Mathematics Stack Exchange (synchronized hourly), though you earn separate badges. You must have 5 reputation to participate on meta.
See also: http://meta.math.stackexchange.com/questions/10765/does-voteup-down-in-msemeta-affect-...
Meta has no impact on your main reputation. Instead, your meta rep is exactly your main rep, with any discrepancy caused only by a small latency between rep changes on main being updated to your meta account.