What's the difference between the pro and the non pro?
First the price... But the Pro is not a nice amount faster (though it's hard to say you'll really feel it), uses a newer and better manufacturing process which can result in more reliability, uses somewhat less power, has a longer endurance (which means that it can live through more read and writes), and has 10 year warranty instead of 5 for the Evo.
That all said, the Evo is still one of the best value SSD drives, bring great and still not that expensive.
Just not to leave it without mention... There's also the M.2 (which uses a different interface straight to the motherboard unlike the old SATA drives) line from Samsung, the 960 Evo and 960 Pro, which are even more expensive, but a lot a lot higher speeds.