Its human nature that reading and writing something in a language that we know is more convenient. Like, we all feel comfortable while communicating in our regional language or mother tongue. But sometimes a situation arises when two people are supposed to communicate with each other where neither of the two understands each other’s language. Then in order to make communication effective and understandable, we need a translator or interpreter (an intermediate person between the two) that facilitates meaningful conversation.
Similarly, when programmers are asked to write programs, then they prefer to write in one of the available high level languages. But on the other hand, computer is able to understand only machine level language (language of 0s and 1s). Thus, in this case language processors are required to process a program written in some high level language so that it is easily understood by the computer.