Computers can understand instructions if those instructions are written in machine code, meaning long patterns of ones and zeroes. Writing a whole program in machine code would take a long time, so instructions are written in special programming languages that are easier for people to understand. The computer converts that into "computer form" instructions (in other words, machine code) so the computer can follow them. The instructions can also be written in an assembly language, which is almost the same as machine code but a little easier to understand.