If the verb in the predicate is transitive, it must have an object to complete its meaning. Consider the sentence, ‘I bought a pen’. The words I bought by themselves do not make complete sense. But the sentence ‘I bought a pen’ expresses a complete thought. Here ‘a pen’ is the object of the verb bought.

Kinds of object

The object-word is always a noun or noun-equivalent.

He bought a house. (Here the object is the noun house.)
We all respected him. (Here the object is the pronoun him.)
We should help the poor. (Here the object is an adjective used as a noun.)
She tried to escape. (Here the object is the to-infinitive to escape.)
I love singing. (Here the object is the gerund singing.)
The minister promised to look into the matter. (Here the object is the phrase ‘to look into the matter’.)

An object-word may have attributes. Study the following sentences.

He shot a tiger. (Object: a tiger, object-word: tiger, attribute: a)
I have only a vague idea about it. (Object: vague idea, object-word: idea, attribute: vague)
I looked at the boy’s face. (Object: boy’s face: object-word: face, attribute: boy’s)
I met the manager himself. (Object: manager himself, object-word: manager, attribute: himself)
I heard him shouting. (Object: him shouting, object-word: him, attribute: shouting)