About a year ago, on Facebook's (NASDAQ:FB) third-quarter 2014 earnings call, CEO Mark Zuckerberg talked about the company's next generation of products. He mentioned Instagram, Messenger, WhatsApp, and Search. Search? Yes, Search!

Source: Facebook.

During the call, one analyst questioned what his plans for Search were, and Zuck dodged the question. But in more recent calls he's given updates on the company's progress with search. Most recently, the CEO told investors that Facebook sees more than 1.5 billion searches on its platform every day.

In the past year, the company has revamped Search, and it started indexing posts and enabling users to search for items that they missed in their News Feeds. Now, the company has completely indexed all 2 trillion of its users' posts, and the entirety of its archives are searchable. This capability makes Facebook's search function a formidable threat to Twitter (NYSE:TWTR) and Alphabet (NASDAQ:GOOG) (NASDAQ:GOOGL).

Personalized search results
When you search for a topic on Facebook, it takes into account everything you've ever done on Facebook, from who you've become friends with to every article you've posted to what Pages you like. It can all have an impact on what content makes it to the top of Facebook's search results. If Facebook knows you like a certain publication, it may be more likely to post that article at the top of results, with comments from your friends.

Facebook search results are a lot like the desktop version of Twitter's Moments, but more personal. If I wanted to follow Hillary Clinton's Benghazi testimony, for example, I might also want to know what my friends and favorite pundits have to say about it. Moments can't guarantee that either will be in their feed, but it's a sure bet that both will be in Facebook's search results.

More importantly, Facebook's search is now capable of competing directly with Twitter's search. And with more people posting about news on Facebook than ever, that makes it a formidable competitor. Consider that 63% of Facebook users say that they get news from Facebook -- the same percentage as Twitter. With improved search capabilities, that number may increase for Facebook, reducing the importance of Twitter for some social-media users.

What's more, Facebook could take share away from Google. Google recently announced that people conduct more searches on smartphones than on desktops, and Facebook absolutely dominates time spent on smartphones. If users feel they can get all the information they need on Facebook -- and get more personalized results -- Google stands to lose some of those search queries.

With the recent expansion of Instant Articles, Facebook could deliver a more pleasurable mobile search experience than Google. Google has responded to Instant Articles with its own open-source project, Accelerated Mobile Pages, but it has yet to see the strong adoption rates of Instant Articles.

Search could mean big money
There's a reason Google's search advertising business has grown so big: Keywords are one of the easiest and most effective ways to tease out immediate intent. If I search Facebook for Halloween costumes to find out what's popular this year and what my friends are planning, I might want to see an ad for Halloween costumes.

Facebook says it doesn't currently have any plans to monetize search, but analysts at BAML stated their belief that search advertising on Facebook is a $5 billion opportunity, following the revelation that Facebook receives 1.5 billion queries a day.

Facebook is already pushing heavily into the most valuable vertical for search -- shopping. It's rolling out a dedicated shopping feed that includes products from Pages that take advantage of its new shopping tab. Users will be able to search for specific products at the top of the shopping feed. That search bar represents an excellent place for Facebook to start monetizing search on its platform.

It remains to be seen how users will respond to Facebook's new search capabilities. With the growing number of users viewing Facebook as a source for news and information, however, it has a lot of potential to attract the audience Zuckerberg is looking for. Last year, he said things don't really become interesting as a business for Facebook until about 1 billion people use them. Facebook search has some way to go, but it's definitely much improved from where it was a year ago.