The document discusses modal verbs in English. It defines modal verbs as auxiliary verbs that provide additional meaning to the main verb, such as can, could, may, might, must, have to, should, and ought to. It then explains how modal verbs are used and formed, what tenses they have, and what meanings they express, such as permission, obligation, possibility, and ability. Examples are provided throughout and exercises ask the reader to select the correct modal verb for different situations.