I think I need help understanding this more clearly?

There are several degrees of politeness in the Japanese language, and this is reflected in the grammar. "masu" is the suffix of neutral-polite, affirmative form of the verb in the present tense, "masen" is the suffix of neutral-polite negative form. It is possible to say "taberu" meaning "I eat", but this will sound impolite, so "masu" is added. "taberu" is used in phrases, e.g. "taberu koto ga dekimasen" = (I) can't eat