Is there social security in Mexico?

I was wondering if Mexico has social security for its citizens and the basics about it.

How old do you need to be to start collecting?

How many years do you need to have paid into it?

Can you collect if you live out of country?

Is there any requirement to have lived in Mexico recently?

If you have a link to a government webpage with more info that would be great. Spanish is ok for the link.

Thanks.