What: Shares of social networker Facebook (NASDAQ:FB) have soared today, up by 15% as of 12:20 p.m. ET, after the company reported strong fourth-quarter earnings.

So what: Revenue in the fourth quarter jumped 57% to $5.8 billion, driven by continued growth in advertising sales. Adjusted net income came in at $2.3 billion, or $0.79 per share. Both top- and bottom-line results utterly crushed the consensus estimates of $5.4 billion in sales and $0.68 per share in adjusted earnings.

Now what: Facebook continues to grow its user base, which now stands at 1.59 billion monthly active users. Of these users, 1.44 billion are mobile monthly active users. The company generated nearly $2.1 billion in free cash flow during the quarter, and $6.1 billion in free cash flow throughout all of 2015. Mobile ad revenue comprised 80% of all advertising revenue in the fourth quarter, as Facebook continues to execute impeccably on the mobile front.

Evan Niu, CFA owns shares of Facebook. The Motley Fool owns shares of and recommends Facebook. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.