Many English exams have fill-in-the-blanks questions. These blanks need to be filled with the forms of the verb "to be". What is meant by the "to be" verb form. Does it mean only the word - "to be". How come is/are/was/were comes into the picture when you say "to be". Does something more come to mind when we say "to be" form?
I see that you are from Bangalore, India.
So, in Hindi, 'to be' verb means "होना". And that's how, 'is/are/was/were' comes into the picture.
The boys is moving toward the school bus -incorrect
Boys "का मूव होना" is correct but then 'to be' verb should be 'are'.
The boys are moving...
The subject-verb is important in this as singular goes with singular verb and plural with plural.
This is the shortest way I could make you understand with the help of Hindi. Further reading is strongly recommended. This will be helpful.
The verb "to be" has a complex history.
There were four different verbs in Old English: 1. "Beon" meaning to exist 2. "eom" meaning to remain, (mostly used in the present tense) and 3. "wesan" (which tended to be used in the past tense) and meant dwell 4. "earun" (A northern dialect word meaning to exist) There was also a prefix "es-" that also could be used to indicate that something existed.
These four expressions have become mixed and tangled into what we now think of as being a single irregular verb, with the following forms:
infinitive to be present participle being past participle been present past first person present I am I was second person present you are you were third person present it is it was plural we/you/they are we/you/they were
It is a mess: five different words mixed into one. But you have to choose the correct form, based on the grammar of the sentence. When asked to pick a form of "to be" it is asking for one of these
to be is the infinitive form of this verb, all other forms you mentioned they are just grammatical forms of this verb. For example am/is/are the present forms. You cannot say I to be...: you say "I am...". You ask about the meaning, there are many meaning because this verb can be the auxiliary, the part of phrases etc. This is very wide-spread word, thus, it looks for you that it is very often appear in some exam tasks.