In simple words programming language can be explained as a language which is used to write instructions or programs for a computer to understand. Computer cannot directly understand the programming language. For making it into a machine understandable language there is a complier and linker which translate these programming languages to machine language which a computer can recognize and understand.
Many applications in different sectors or industry are developed by these programming languages. Each industry has its own requirements and with the help of these programming languages applications programs will be developed. On running these application programs on the system their requirements will be fully achieved. This is how most of the companies run their systems.
For example when you log in to a bank site you can see a screen. During log in an application program runs in the back end and throws the screen in front of you. Similarly each click on the screen will execute an application program at the back end. And these application programs are developed using programming languages. As everybody knows computer performs many functions but how it does by just pressing a key?
The answer is a program runs behind when we press a key. These programs give computer step by step instruction on what to do. And the language with which we give instructions to the computer is the programming language. There are many programming languages. Some of them are C, C++, COBOL, JAVA etc. In the initial days when programming languages were found the main languages that were in use are BASIC, FORTRAN and COBOL.
Later on many new languages C, C++, JAVA etc came into picture. Among all these Assembly Language and Machine language are a bit different. Understanding the keywords of all the other languages is very easy because the keywords are in English. But in these languages you can only see 1s and 0s. This can be read and recognized only by machines.