Card draw refers to effects that put additional cards into your hand, giving you more resources and options over the course of a game. Because players normally draw only one card each turn, effects that generate extra cards are a fundamental source of card advantage.
Esper Sentinel can reward you with cards when opponents cast certain spells, Beast Whisperer keeps creature-heavy decks stocked as they cast more creatures, and Wheel of Fortune replaces everyone's hand with seven fresh cards at once.