A lot of these answers are incomplete.

Let’s say you run a profitable publicly traded business. Each year you will have some of your profit leftover after you pay for the costs of running the business and what not. Now you can try to reinvest all that cash back into the business in the hopes of increasing future returns and growth. Give employees raises and open new stores, research new production methods and tech, etc.

At some point you really can’t effectively reinvest in the business. Not every dollar reinvested will have a good return. So what do you do with the money? You can pay out a dividend to shareholders, buy back your own stock or purchase another business. Each of those have upside and downside and a good management will consider all of those before choosing one. Dividends used to be much more popular but the perception has changed over time. Some people don’t like the idea of having to pay taxes on this money instead of letting it grow. Buybacks are a middle ground. By decreasing the outstanding shares, the other shares become more valuable as their piece of the pie becomes larger. They aren’t taxed on the gains since they haven’t really received them. One issue with this is that buybacks when a stock is overpriced is not usually prudent and probably would have been better distributed as a dividend.

I believe the negative perception of stock buybacks has to do with an incomplete understanding of free cash flow from productive businesses and the limited options they have to use this money intelligently