The Hand in the Yu-Gi-Oh! TCG and OCG is the amount of unplayed cards in your possession that you have drawn from your Deck or otherwise. As implied, you would generally be holding these cards in your hand. You are generally, but not limited to the following, able to Normal Summon or Set the Monsters in your Hand, set the Trap cards in your hand, and Activate or Set the Spell cards in your Hand.
During your Draw Phase after you draw a card it is added to your hand. The hand size limit is six, so during your End Phase if you have more than six cards in your hand, you must discard cards until you have six cards left. Hieroglyph Lithograph extends the hand limit to seven cards, while Infinite Cards removes this limit for both players.
Certain cards can interact with cards in either yours, your opponents, or both sets of hands. Spirit Reaper can discard 1 card from your hand as part of it's effect, and Exchange allows you to swap one card from your hand with one card in your opponent's hand.
Types of Monster Cards
Types of Spell Cards
Types of Trap Cards
ATK • DEF • Level • Attribute • Type
Playing Field Zones
Types of Summon
Types of Monster Effects
Types of Effect Monsters
Types of Spell Speed
Aqua • Beast • Beast-Warrior • Dinosaur