Bob Smalser wrote he was once asked: “Butt chisel vs. bevel edge chisel—how are they defined and what's the difference? Mortise chisel vs. sash (?) chisel—again, how are they defined and what's the difference?”
Find the article on WC where he elaborates on this for beginners, with photos. Copy-paste the URL if you find it.
Hint: Use the Search link in the upper-right corner of all pages.
Butt, bevel, mortise, and sash chisels
Edited #1