KA1 is a metal alloy composed by Ferritic Iron, Chromium and Aluminium alloy; is the most common wire, with low costs, is currently used in straight wattage mod, with an average ramp-up time, is able to hold his shape and to clean, giving to coils a longer lifetime.
Ni80 is composed by Nickel and Chromium, heating up faster than Kanthal.
It also holds well his shape making it easier to wick; unfortunately, it has a low melting point making it not suitable for high wattage as the coil could break.
SS316L, a metal alloy made with Chromium, Nickel, and Carbon is graded for medical and pharmaceutical uses.
This means it has been tested and certified and is safe to vape with, it has similar characteristics to Nichrome as it heats faster than Kanthal, but with a higher melt point.
The only downside to Stainless Steel is the cleaning point, as dry burning, will deteriorate the coil.
We then have different types of complex coils that are usually categorized in Clapton, Fused Clapton, Framed Staple Clapton, Aliens, Braided and Juggernaut.