The document discusses the present tense forms of the irregular verb "to be", which are "am", "is", and "are". It explains that these can function as either a main verb indicating a state of being, or as an auxiliary verb used to form verb tenses together with another main verb. When used as a main verb, it links the subject to an adjective without an object. Examples are given like "Emma is a teacher" and "The eggs are in the fridge". When used as an auxiliary verb, it has no meaning itself but performs a grammatical function, as in forming the present progressive tense.