Voting happens at the annual-meeting or a special meeting, and almost all retail votes are cast by proxy card rather than in person. The items on the ballot are described in the proxy-statement. Only holders on the record-date may vote.
Voting rights are what make a proxy-fight or a hostile-takeover possible at all. If you hold in street-name your broker passes the ballot through to you, and uninstructed shares can no longer be voted by the broker on contested items.
Example: a company with 200M shares needs 100M plus one for a simple majority. An activist owning 14M shares does not win on its own votes; it wins by persuading index funds holding 60M shares to side with it.
Related: proxy-statement, proxy-fight, record-date, street-name