IANA Wall Streeter, but IIRC - the “proxy” means you allow a designate to vote your shares. Rarely does this figure into board actions, unless the people in control of shares give their proxy to someone who then gets a significant fraction of the shares.
I.e. Bob and Ted and Carol and Alice and Englebert all have 20% of the shares of Widgets Inc. For the shareholder meeting, Bob and Carol give thier proxy to Ted, since he seems to know what is best for the company (Or they can’t make the meeting). Ted now has, with his votes, 60% of the shares and can pick the board members etc. at a meeting of the company.
The board is empowered to act to decide what the company will do. Thanks to Fisky-type shennanigans over the years, there is a list nowadays of actions which require shareholder approval, either at a special meeting or the mandatory Annual General Meeting. Nowadays, IIRC, issues of additional shares requires shareholder approval. If it can’t wait until the next AGM, a special vote may be called for. You can submit either a proxy vote (I want my shares voted this way) or assign a proxy (Ted will vote my shares).
When a person intends to acquire more than 10% of a company’s stock, nowadays, for publicly traded companies on stock exchanges, he must declare his intentions. You can’t secretly buy up a controlling interest like Vanderbildt. It is even an indictable offence to collude with someone else, to each take over 9.9%; and when you intend to buy a controlling interest, you must make an offer to all shareholders. When more than 50% sell to you, the ohers are entitled to also sell you their shares at the same price. You can’t say “I got my 51%, I’m going to milk this company until your 49% are worthless!”. (Minority shareholder protection).
A common “poison pill” which is a measure to thwart hostile take-overs, is to dilute the rest of the shares. Cornelius has bought 20% of the shares, thus triggering the plan (approved by the shareholders at an earlier vote). It might be something like - everyone except the hostile bidder get 2 shares for 1 - thus adding 80% more shares, effectively making the original 20% investment worth half what it was. For companies valued in the hundreds of millions or billions, flushing half of a hundred million or more down the drain is a bad start to a takeover.
OTOH, if you are Joe Schmoe and own $20,000 of Widget-Acme shares, odds are a takeover battle would boost that price by 50% to 100%. (IIRC RJR-Nabisco went from $50 to $107 during their epic battle). Why would you accept a plan that discouraged a bidding war just because it was hostile to the existing management?