What is the difference between volatility and evaporation?
Evaporate is a phase change from liquid to gas without changing the molecule itself (or the atoms is the liquid is atomic). 

Volatility is essentially the tendency of a liquid to evaporate. So a highly volatile liquid would show a great tendency to evaporate.  

A measure of volatility is the vapor pressure. There is a very related term partial pressure. So if we think of air as being nitrogen and oxygen, then there is a partial pressure for nitrogen and a partial pressure for oxygen, and the sum of the two partial pressure is the actual pressure (the absolute pressure).  

To make things a bit more confusing chemists think of absolute pressure. So because we are in earth's atmosphere there is always 1 atmosphere of gas pressure. So when you pump a car tire up to 30 lbs/sq inch, there is already 14.7 lbs /sq inch air pressure due to the atmosphere. So the absolute pressure inside the tire is 44.7 lbs/sq inch.