Heal can appear as certain activation, or with a chance to activate. It can activate on Entering Play, on leaving play, or during the card's turn. It can target itself, one, several or all of your creatures, and it may target a specific race. The heal amount can go from 1 to 6. There are special abilities for Healing on Attack and Healing on being attacked, as well as an ability that heals your Vampire Lord.
Heal works well on creatures with lots of Health, and even better on creatures with the Brothers in Arms ability !