A stock buy back, which Apple does all the time, is simply a way for a company to directly return money to specific shareholders who want "out". Those are the folks selling their shares. Many Apple shares are sold every day, an equal number are bought. That is why we have stock prices. Apple does buy backs and then retires the shares (i.e., those shares will no longer get dividends and they won't be voted in shareholder votes for the board of directors). So the remaining shares now have a slightly larger percentage of the future dividends and asset value of Apple. So they are slightly more valuable. Apple specifically reduces the supply of publicly traded shares.
Companies do this instead of sending out dividends mainly because dividends get taxed. Also there are historical and market reasons that a company does not want to ever decrease their dividend. The stock market price of a company that does that gets immediately reduced. So companies tend to be very conservative about what their dividend is and they set it at a level they are very confident they will always be able to pay. Each decision to raise the dividend is weighed against the risk of ever not having enough available cash to pay it in the future years. Apple pays a modest dividend. But has had so much cash coming in for so long, they started doing stock buy backs.
so buy back is used to raise share value instead of giving dividend out right so they don't get taxed? thats it? thats the reason?