The PC only understands a language called machine code. This is very human-unfriendly and difficult to program in. It takes many lines of machine code to do a very simple task. This is because each command in machine code is very simple.
Consider adding two numbers together, 1+2. This takes a number of machine code commands to do. First of all it must load the number one into the CPU. It then must then load the number two into the CPU. Finally, once both numbers are in the CPU, it can add them together.
Load 1, R1
Load 2, R2
Add R1, R2
R1 and R2 stand for register one and register two. We shall look at registers in more detail later.
Machine code is too complicated for humans to code much in. As such we use other programming languages. To add 1+2 in visual basic would be
Answer = 1 +2
This is much simpler. However the CPU does not understand this language. So a translator must be used. The job of the translator is to take what the programmer has written and convert it into something the CPU understands.