It’s no secret that mobile is the way of the future. Just look at the more than 190% jump in Facebook (FB) stock since it proved its chops at mobile back in the summer of 2013.

But what does it take to make a successful app? Are certain categories more popular than others? Do free apps do better than paid? We went to the experts for answers.

Gian Fulgoni co-founded comScore which tracks all things digital, including apps. According to their research, the most-used apps fall into three categories – social apps like Facebook, gaming apps and radio apps. “Those three account for about half of all time spent with apps.”

So what does that mean for companies?

Well, the most popular apps come from the usual suspects. Facebook, Google (GOOG), Apple (AAPL), Amazon (AMZN), eBay (EBAY) and our parent Yahoo (YHOO) account for 9 of the top 10 most used apps (the other is Pandora - P). The same six account for 16 of the top 25 apps and 24 of the top 50. So the same hierarchy that exists on desktops has translated to mobile. (Nielsen, which also compiles this data, has come up with similar results. Their top 10 apps of 2014 can be found here.)

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With this kind of dominance in play, is there any hope for the little guy? Can start-up apps break in and disrupt the market? We asked Fulgoni. “I think a lot of people are asking that question,” he said. “I’m not sure there’s an easy answer. It’s just become a marketplace where a lot of people are trying to come up with new ideas for apps. So there’s a lot of competition.”

By “a lot” Fulgoni means well over a million apps available on iTunes and Google Play. (Those stores, consequently, are also considered apps and rank in the top 10.) The challenge exists in not only making an app that people will want to download, but then convincing people to use it once its on their smartphone or tablet. People tend to only use one or two apps consistently. According to Fulgoni, “We’ve found that the most popular app on the phone accounts for about 40% of the time spent with the phone. And then the top four apps on the phone account for about three quarters of time spent on the phone using apps.”

Related: How Facebook (and Twitter) are mastering mobile

In terms of what that means for developers: “It’s really a double edged challenge. You’ve got to get the app on the phone but then even once you’ve got it there the challenge is whether people are going to pay attention.”

Certain types of apps lend themselves better to mobile. For example, people are more likely to use maps and weather apps on mobile devices. They’re more likely to use retail, news and search programs on a desktop.