Flutter is an open-source UI software development kit created by google. It is used to develop cross-platform apps for IOS, Android, Mac, Windows, Linux, and the web from a single codebase.
The programming language that flutter uses is called dart. It is a fairly easy language to pick up but there are not many resources available on the internet for people who are completely new to the world of programming.
Since the flutter code can be compiled into JavaScript, it is possible to have the same codebase(as per the developer preference) for Android, IOS, and the web version of an app.
Yes, react native is better than flutter because React Native developers are also React developers, and React happens to be the most popular front-end framework out there. But the speed with which flutter is improving, it will take over react native in no time for sure.
P.S: This is my first ever article, looking forward to publishing more articles like this in the future.