Rest is a Magic recovery move that allows a Ponymon to recover from HP damage and status problems , however, the Ponymon remains asleep for two turns and cannot attack during these turns. Ponies can still take damage while they're asleep.
YApplejack - Lvl 19
"The user sleeps for two turns to fully restore HP and heal any status problem."
DISCLAIMER: More ponies may need to be added with further expansions.