There have been hundreds of programming languages since the start of computing. Now as the years go by, new languages do come along. Some are big hit but most of them aren't. So this list changes, but it changes slowly.
Now most programmers will learn and use many languages over the course of their career. Once you have got the basics down, additional languages do become easier to pick up. But if you're new to this, you might think why, why are there so many languages? If all we're doing is writing simple instructions for computer, why isn't there just one computer language? Well actually that language does exist, but it isn't any of these.
We might informally say when we are programming that we're writing code the computer understands, but we are not. You see the only thing that chip understands his called machine code or machine language. Now these are the real instructions that run directly on your computer hardware.
So the question is why don't we just write machine code? Well because it's almost impossible to do. It's numerical operations, tiny instructions that work on the smallest pieces of memory inside your computer and even if you could write it, it's basically unreadable by anybody else.
This is for the machine. It's not for a human being. And because machine code works of the level of the CPU, it would be different machine code for different models of CPU. Writing a full program in machine code would be like digging a tunnel through a mountain with only teaspoons.It's theoretically possible, but it would take you so long and so tedious that you wouldn't even try. They are invented languages. They are just trying to bridge the gap between us as human beings and the computer hardware.
Now, some of the languages are actually quite close to machine code. The closest is something known as assembly language. In general the closer a language is to machine code the more difficult it is to write and the more you have to know about the actual hardware. And this what's called a low-level language. Now as you move away from the CPU into what are called higher-level languages you worry less about the hardware. Now this code is often easier to write and to share even across different platforms, but it can be slower when running because these languages aren't necessarily optimized directly down to the CPU level.
But whatever we write has to be converted down to machine code before it can run. Sure we do need to know that's what runs, but programming for us is all about the source code. That's what we call the statements we write, Java, C++, Ruby, Python whenever. We write the source code that will at some point be translated then into machine code, so it can run on the computer.
We need to understand three things:
1) how to write it, literally where do we actually start typing this
2) to understand how that source code will be converted to machine code, and
3) how do we actually run it, how do we execute our program? And some of this does depend on the language that we pick.