The two big categories of front end development are Web and Mobile.
Mobile developers build all the awesome apps you have on your iPhone or iPad. Or if you’re stubborn on your Samsung or whatever Android phone you have. These are apps with an icon that you have to download from the App Store and update when there's an update available. These are also called native apps because they're written in a language native to a platform like iOS or Android.
The Web is a little different. It's all the websites in the world that you can access using a browser on any device, your laptop, phone or tablet. They don't need to be installed and you don't download any updates for them. You just simply type in the address and you're good to go.
It's been a long difficult debate about which type of app is better. Mobile or Web. Very mature, guys...
But there are plenty of good reasons to build both kinds. Developers use similar but different technologies to build apps.
You might ask why can't we use the same technologies to build for both mobile and web. That would make sense wouldn't it?
The short answer is that the two platforms evolved separately at different times with different intentions, and some tools and technologies are just better for certain jobs. You wouldn't use a hammer to screw something to the wall, you would use a screwdriver. So think of different programming languages as good for what they were intended for, and nothing else.
It doesn't have to be a lifestyle, as so many developers make it to be. Again, very mature, guys...