Share buybacks. Share repurchase. Stock buybacks. Stock repurchases. It may go by any of these names, but the concept is the same: when a company asks its stockholders to tender the shares that they own for repurchase by the company, using cash. The shares that were repurchased will still be part of the equity of the company, but reclassified as Treasury Stock or Treasury Shares.
Companies that find themselves with excess cash have a number of options available to them with regards to what to do with that extra, unutilized cash. They could either reinvest it in securities or make major acquisitions, or they can increase the cash dividends that they pay their stockholders. Or they can opt to repurchase their shares that were previously issued.