Is Facebook part of Google?

Zuckerberg explained, Google is purchasing 98.4 percent of Facebook, leaving Microsoft with 1.6 percent ownership. “We feel this accurately reflects Microsoft’s market share in the Web 2.0 economy,” Schmidt said. Schmidt noted the many synergies between Google and Facebook that led to the deal.

How can two companies buy it?

It is done through a contract. Or shares depending on their agreement.