Grammar is the glue that binds words together to create large units with meaning. There are many differenet views and explanations of how English grammar works. A grammar is an individual description of the rules of the structure of a language; the way words combine, the order they come in, the way they change according to their relationship to other words, how they build up into units like a sentence etc. However, there is no single definitive set of rules. There are strong differences of opinion over many basic concepts such as how many tenses there are in English. There are also a lot of similarities in the different descriptions- grammars generally agree on things like word order, which is an important part of English grammar.