I again want to take you guys back to school, where we learned grammar. Now tell me why you learnt grammar Do you really need to learn grammar? The answer is definitely yes! When we grow, we learn our native languages. Now, when we typically learn languages, we learn a small set of vocabulary. We learn to combine small chunks of phrases and then small sentences. By learning each example sentence, we learn the structure of the language. Your mom might have corrected you many times when you uttered an incorrect sentence. We apply a similar process when we try to understand the sentence, but the process is so common that we never actually pay attention to it or think about it in detail. Maybe the next time you correct someone's grammar, you will understand.
When it comes to writing a parser, we try to replicate the same process here. If we come up with a set of rules that can be used as a template to write the sentences in a proper order. We also need the words that can fit...