The first conditional is used to talk about possible future situations and their possible results.

http://www.bbc.co.uk/learningenglish/english/course/lower-intermediate/unit-23/session-2/activity-3

Linking devices are used to link one idea or argument to another. A common situation is when we are talking about something that happens and its result, or a cause and its effect.

http://www.bbc.co.uk/learningenglish/english/course/intermediate/unit-10/session-2/activity-3

The second conditional is used to talk about impossible, unlikely or imaginary situations and their possible results.

http://www.bbc.co.uk/learningenglish/english/course/lower-intermediate/unit-24/session-2/activity-3

Zero conditional is used to talk about things which always happen in particular situations.

http://www.bbc.co.uk/learningenglish/english/course/intermediate/unit-5/session-2/activity-3