What is MAST, and how will it benefit bitcoin?
it stands for "Merklized Abstract Syntax Trees." bitcoin magazine did a pretty good introduction
here. in the simplest terms, it's a proposed addition to bitcoin (finally formally proposed on the mailing 3 months ago) that can allow for smaller transaction sizes and more privacy. more efficient implementation of smart contracts is a big part of it.
here's a simplified rundown
from Mark Friedenbach:
An abstract syntax tree is a computer science term for the parsing of a programming language into a tree like structure, where for example an "if" condition would be a parent node and the two branches (if/else) the children. The MAST idea was that if you hash both branches you can then choose to only reveal the branch you take, gaining a possible space savings and more importantly an increase in privacy as observers don't see the other branch.