Many of them don't know about this app,
This is a computer software that allows you to create your own android applications.
Yes, with the knowledge of java, xml you can create apps here. It is not so easy but after learning step by step, you wont find it difficult.
Its bit tricky to install as there are many files that need to be installed and stored at a particular place. This is where people find some difficulty.
Once everything like java jdk, emmulator, etc are all installed you can start coding, debugging, creating apk, making a app of your own.
But you need to learn java first.
It is the official IDE for Android application development, based on IntelliJ IDEA. On top of the capabilities you expect from IntelliJ.
There are many ways of approaching app development but android studio is most powered, popular and the best one.
So if you have java skills and want to make some cool apps, the grab your pc and download android studio now.( watch some tutorials for how to install android studio) .