The document discusses modal verbs in English. It provides definitions and examples of different modal verbs including can, could, may, might, must, ought, should and will vs shall. It explains how modal verbs are used to indicate modality, cannot work alone but require a main verb, and do not take "-s" in the present tense. Examples are given for different uses of each modal verb like ability, permission, possibility, necessity, obligation, advice and expectation.