Facebook has built a multi-billion dollar ecosystem with its application platform, but much of the growth of that platform has been driven by social games created by companies like Zynga.

In an effort to help the 900m-plus Facebook users discover apps of all shapes and sizes, and create new monetization opportunities for app developers, Facebook yesterday announced the launch of its own app store, the App Center.

App Center, which will be rolling out to Facebook users in the coming weeks, looks a lot like the app stores operated by companies such as Apple, Google and Amazon.

As one might expect, it features directories of apps broken down by categories, which include Games, Lifestyle, Music, Sports and News, and each app that’s in the App Center has its own developer-populated page showing details about the app as well as screenshots.

The App Center is more than just an app directory, however. In an effort to entice developers into developing apps beyond social games (and increase the number of ways Facebook can profit from its ecosystem), Facebook is beta testing paid apps.

These Facebook apps, like apps sold in Apple’s App Store and Google Play, will require users to pony up cash (most likely in the form of Facebook Credits) before they can be installed.

The world’s largest social network is also focusing on driving the growth of apps through mobile. As Facebook’s Aaron Brady explained,

The App Center is designed to grow mobile apps that use Facebook – whether they’re on iOS, Android or the mobile web. From the mobile App Center, users can browse apps that are compatible with their device, and if a mobile app requires installation, they will be sent to download the app from the App Store or Google Play.

This may prove to be the most important aspect of the App Center. With more and more users accessing Facebook from mobile devices, mobile presents huge opportunities for Facebook. But right now it’s also the source of frustration for the soon-to-be-publicly-traded company, which yesterday amended its S-1 to further highlight the challenges it faces in monetizing mobile usage. And monetization isn’t the only problem: a growing number of companies that once focused on social games are shifting their attention to mobile games.

Ensuring that the App Center is mobile-friendly won’t immediately solve Facebook’s mobile problems, but it hints that the company will increasingly treat mobile as a first-class citizen when developing new features.