Present Perfect

Present Perfect is a mix between present and past. It's used for actions in  past that are important in present

 Structure

afirmative sentences: 

subject + auxiliar verb (to have) + past participle + complement

negative sentences

subject + auxiliar verb (to have) + not + past participle + complement

Examples

My Chemical Romance has been considered as the equivalent of The Who for 'Facebook Generation'

Mr Peña Nieto hasn't been the best president in Mexico History

Catholism has been the most followed religion in the world for about 5 centuries

Dodo birds have been extinted for 4 centuries

I have thought about what's after death a lot of times