Facebook lite was first introduced on Android device few years back, and right now as well iOS users can now have the full access to download the app on their device but only for turkey users but the company said the app is under testing and will roll out soon for all countries globally.
The new Facebook for iOS comes in smaller size (5mb) and it uses less battery, bandwith and device storage. The most painful thing about the new Facebook lite is that, the app has not yet been launch globally for all countries except Turkey users.

According to Facebook, he said! not the only app that's gotten a "lite" version recently. Twitter, Messenger, YouTube, and Skype all offer "lite" versions for Android phones.
A Facebook spokesperson provided this statement:
"We're always working to help people share and connect with their friends and family regardless of where they are accessing Facebook. When we first rolled out FB Lite as a standalone app, our goal was to deliver the power of a native app, with as many of the same features as possible while still being lightweight. Up until now, FB Lite has only been available on Android and now we're testing the experience on iOS. We're committed to connecting people with the things they care about - no matter their connection, device, or where they live."