Verbs

Verbs are the action words in a statement. They tell what is happening - what a noun is doing or what is being done to it, or the state of being, becoming, thinking or feeling. A verb with a subject, which will be in a particular tense is a finite verb. Without a subject it will be the infinitive form (for example, to think, to dream) or a gerund (the present participle, used as a noun: smoking is bad for you).
When a verb denotes what a noun is doing, the noun is said to be the subject of the verb: The man speaks. (Here man is the subject of the verb.) When the verb denotes what is being done to a noun, the noun is the object of the verb: The man eats jelly. Here the noun jelly is the direct object of the verb. Verbs can also take indirect objects: Parents give children toys. In this sentence, toys is the direct object, (what is given) and children is the indirect object. The parents do not give children; they give toys.


Verbs that take objects are called transitive verbs, and those that normally do not take an object are intransitive verbs (but note that an intransitive verb may be used transitively in non-standard speech or writing). Some common transitive verbs are: tell, give, show, eat, buy, take, and see. Some verbs can be both transitive and intransitive: Tell a story (transitive), and Time will tell (intransitive). Verbs like sleep, walk, rest, come, and go are nearly always intransitive. The most common verb of all, to be, is intransitive in all of its forms: am, are, is, was, were, and been.





Tenses (time signals): Verb tenses tell the time when an action takes place. Any action or condition may be in the past, present, or future: he was, he is, he will be. Most common verbs simply add an -ed to show the past time, or form the past tense, as it is normally called. Thus walk becomes walked. Other verbs, sometimes called irregular (or strong) verbs, do not add -ed. Instead they undergo an internal change: sing, sang, sung; fly, flew, flown; go, went, gone.
Auxiliary verbs: In the sentence She will sing even though he cannot stay, the verbs will and cannot are called auxiliary, or helper, verbs. Other auxiliary verbs are the incomplete or modal verbs: can, could, may, might, shall, should, and would.
The various forms of the verb to be can also be used as auxiliaries: I am going. He was singing. They have been shopping. The verb have - and its other forms has and had - are also common auxiliaries to indicate past action.
Participles: The verb form used with auxiliaries is the participle. There is a present participle, talking, and a past participle, talked. Thus, a person can say either I talk (present tense) or I am talking (present continuous) to show present action and I talked (imperfect), I have talked (perfect), or I had talked (pluperfect) to show past action. When a present participle is used with an auxiliary verb, the purpose is to show continuing or ongoing action. She is doing the laundry. He was speaking when someone interrupted him. Note that this uses a present participle with a past tense auxiliary verb (was) to indicate continuous past action.





Verb flexibility: Verbs and verb forms can be used in a number of ways in sentences. A verb can be the subject of a statement (To walk is good exercise) or its object (I like to walk). In each case, the infinitive form to walk is used as a noun. Participles can be used in the same way: He likes swimming. Flying is great sport. In the first sentence, swimming is the object of the verb, and in the second, flying is the subject.
Verb forms can also be used as adjectives, or words that describe nouns. In a wrecked car, the word wrecked is a past participle used as an adjective.
Occasionally a verb form or verb phrase can be used as an adverb: He was pleased to meet her. The phrase to meet her modifies the adjective pleased.

source: http://babelnet.sbg.ac.at/themepark/grammar/verbs.htm