system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What are the different programming languages for?

I only know that HTML and CSS are for webpages but completely clueless about the rest. Can they all be used for web pages? Or do they each do a different thing?
gpt
In general all programming languages can all do the exact same thing. They differ in how easy, how fast and how efficient the process of doing the thing is.  
The basic test for what a programming language can do is to see if it can do the same thing as a very simple computer called a "Turing machine" and language or system that can do that is called "Turing Complete". A language that is Turing Complete could do any computation task given an infinite amount of time and memory. This turns out to be a very low bar, for example people have built a turing complete computer inside of Minecraft.  
  
Once that low bar is out of the way the languages begin to differentiate.  
Some languages like Python are super easy to learn, but run really really slow. This allows you to focus on making you algorithm really good, but makes it nearly impossible to fiddle with the nuts and bolts of how the program is run.   
  
Some languages like C are more difficult to learn but run really fast. Alot of the old operating systems were coded in C, because they really need it going quickly.
  
Some language like Java or C++ strike a balance in between them.  
  
Other languages like MATLAB focus on doing one thing and doing it really really fast and easy, but are difficult for other thing. MATLAB does math and graphs really really well, but you would have to jump through some serious hoops to build a game out of it.  
  
Also the languages differ in the "Libraries" that support it. A libary is a collection of code that a programmer can call upon to help him do something. For example rather than writing the code to draw a cube on the screen from scratch, he downloads a library and calls the function in the library to do it for him.