Acquisitions are agreed or hostile. An agreed deal runs through a board recommendation and a shareholder vote; a hostile-takeover goes straight to holders through a tender-offer or a proxy-fight. Either way the buyer pays a deal-premium over the pre-announcement price.
For the acquirer's shareholders the question is whether the deal is accretive-dilutive. Acquirer shares often fall on announcement, particularly in an all-stock-deal, because of the dilution and the integration risk.
Example: a buyer offers $6.0B for a target with a $4.4B market cap, a 36% premium. Funding it with new shares at $50 means issuing 120M shares, expanding the buyer's 900M share base by 13%.
Related: merger, hostile-takeover, deal-premium