How does a company acquire a product of another company?

[I Am Who I Am]

For example, Facebook has acquired Instagram, Adobe has acquired Macromedia's Dreamweaver, Google has acquired Meebo and Android.

Do they just pay them and they have to give away their products?

[CanadaRAM]

One of two ways
1 Licensing: where one company pays for a license to sell the other company's product, or incorporate it into another product for sale. Licensing can be exclusive or non-exclusive.

2 Purchase of the entire company. This is what is usually meant by acquiring, one company purchases another, often with a combination of cash and shares, and then owns the whole company, including all of their technologies, patents and products.

[Neil]

Large companies have stocks & shares owned by 1,2,3 or thousands of shareholders/stockholders.

To purchase another company, the buying company has to purchase the share/stock holding held by the various share/stock holders of the company being purchased. If there are only a few stock holders it can be an easy exercise and is completed in a few days but if there are thousands it could take years before the purchase is finalised.