S4/s5 Long/short Block?
 

What are the exact differences between S4 and S5 motors? Is one a long block and one a short?

long block/short block refers to what comes with the engine. If it comes with the complete intake and exhaust manifold, alt, pumps, etc. it's called a long block. If it's just a bare block then it's a short block. This applies for any motor.

Main differences are the front plates are different, S4's have an EGR, the rest is really internal...S5's are more powerful and have different compression numbers.

oh yeah...you're a noob so this is meant as advice...

Use the search button. It works great.