What is "verb to be" and how and where we can use it?

You have already used the verb "to be" in your question, when you used the conjugated verb "is". Other conjugations of "to be" in English are: was, am, were are, and being. "To be" is called the infinitive (unconjugated) form of the verb. (I never learned this until I studied foreign languages!)

For more about the conjugations of "to be", see

http://www.scientificpsychic.com/grammar/to_be.html

The form that you use depends upon the subject pronoun and the tense (past, present, progressive, past participle or subjunctive). The table at the website above explains it better. The future tense of "to be" is just "will be".

The "verb to be" refers to the English verb "be," which is used to indicate states of being, identities, and relations. It is one of the most important verbs in English and is used in various ways, such as forming simple sentences, creating progressive or continuous tenses, making passive voice constructions, and expressing certainty or possibility.

To use the verb "to be," you need to conjugate it according to the subject and the tense of the sentence. Here is how to use it in different scenarios:

1. Simple Sentences:
- Present tense: I am, you are, he/she/it is, we are, they are.
- Past tense: I was, you were, he/she/it was, we were, they were.
- Future tense: I will be, you will be, he/she/it will be, we will be, they will be.

For example:
- He is a doctor. (Present tense)
- We were at the party. (Past tense)
- She will be happy. (Future tense)

2. Progressive/Continuous Tenses:
- Present continuous: I am being, you are being, he/she/it is being, we are being, they are being.
- Past continuous: I was being, you were being, he/she/it was being, we were being, they were being.
- Future continuous: I will be being, you will be being, he/she/it will be being, we will be being, they will be being.

For example:
- She is studying right now. (Present continuous tense)
- We were working all evening. (Past continuous tense)
- They will be waiting for us. (Future continuous tense)

3. Passive Voice:
- Present passive: am/is/are + past participle.
- Past passive: was/were + past participle.
- Future passive: will be + past participle.

For example:
- The book is written by him. (Present passive voice)
- The car was repaired yesterday. (Past passive voice)
- The report will be submitted tomorrow. (Future passive voice)

The "verb to be" is used in various contexts, including describing people or things, stating facts or characteristics, talking about time and dates, and expressing possession or relationships. It is important to understand the specific rules and meanings associated with each tense to use it accurately and effectively in your sentences.