Like the Gerund the Infinitive possesses some likeness to the noun, which is manifested in its syntactic functions, - the main functions of the Infinitive are the Subject, the Object and the Predicative.
It's necessary to find him at once.
Нужно немедленно найти его.
I like to travel.
Я люблю путешествовать.
The plan was to meet in the forest.
План состоял в том, чтобы встретиться в лесу.
But the Infinitive is a verbal part of speech having some verbal characteristics:
The Infinitive can be modified by an adverb.
I hate to drive slowly.
Ненавижу медленно ездить.
The Infinitive of transitive verbs can take a direct object.
I cannot translate this article.
Я не могу перевести эту статью.
The Infinitive has tense and voice distinctions - it has four tenses in the active voice and two tenses in the passive voice:
Active Passive Indefinite to write to be written Continuous to be writing Perfect to have written to have been written Perfect Continuous to have been writing
The Indefinite Infinitive is used to denote an action simultaneous with the action expressed by the finite verb.
He is said to be a first-rate programmer.
Говорят, что он программист высшего класса.
Note: The Indefinite form of the Infinitive is sometimes used to denote an action which will follow the action expressed by the finite verb.
He is sure to marry her.
Он наверняка женится на ней.
The Continuous form also denotes an action simultaneous with the action expressed by the finite verb but the action is represented as a process here.
He is said to be working at a new program now.
Говорят, он сейчас работает над новой программой.
The Perfect Infinitive denotes an action prior to the action expressed by the finite verb.
They are said to have been great friends once.
Говорят, что когда-то они были лучшими друзьями.
The Perfect Continuous Infinitive denotes an action that began before the action expressed by the finite verb, had been going on for a certain period of time before the other action began and at that moment was still going on.
She is said to have been waiting for him for ten years.
Говорят, что она ждет его уже десять лет.