Consider the case of four persons, Leonardo, Chou, Ivan, Hari, who understand and speak Spanish, Chinese, Russian and Hindi, respectively. To be able to understand each other, they would require some person or persons who could translate whatever is spoken into the language each understands.
Similarly, since there are so many programs written in different computer languages, the hardware also needs a translator to convert the computer language into a form that it can understand.
The computer only understands a language of electrical signals, called machine language.
Software called the compiler converts the computer language into machine language. For example, there is a C compiler that converts programs written in the C language to machine language.