Source: Yugioh Wikia
To draw a card is to take the top card of your deck and add it to your hand. Every turn, you draw one card from your deck during your Draw Phase. Some effects also let you draw cards outside of your draw phase, such as , , and . If you are unable to draw a card from your deck at the start of your turn or by a card effect that requires you to draw a card, you lose. Incidentally, there is a difference between the number of times drawing and the number of cards drawn (see Draw Count).
Allowing your opponent to draw while you are about to win can cost you the duel. This is a common occurrence whenever Yugi or Jaden duels; they seem to struggle in each and every duel but luck out with their last draw to win.
There is also picking up a card, which is not classified as drawing.