Introductory it

When the subject is clause, the sentence usually begins with it. So instead of saying “That he was once a communist is true,” we say,” It is true that he was once a communist.”

Introductory it is also used with seem, appear, and look when the subject is an infinitive phrase, a phrase with a gerund in it or clause.

It looked doubtful whether she would come.
It seemed strange that she should behave like that.
It seems possible that he may quit the job.
It appeared unwise to offend him.

It is sometimes used as the object of the verbs think, feel, deem, count, consider etc.
Don’t you think it dangerous to drive so carelessly?
I consider it a privilege to have this opportunity of welcoming you.

The introductory it is sometimes used in questions.
Who was it that broke the window?
It is Peter who broke the window.
When the subject is an infinitive phrase, the sentence often begins with it. Instead of saying “To find fault with others is easy”, we say “It is easy to find the fault with others.”

When the subject is a phrase that includes a gerund, it is used as a provisional subject to begin the sentence. Instead of saying “Your trying to deceive us is no good,” we may say “It is no good your trying to deceive us.