Trap Cards are cards with purple-colored borders that have various effects.
A Trap Card must first be Set and can only be activated after the current turn has finished. After that, it may be activated during either player's turn. Trap Cards are Spell Speed 2, with the exception of Counter Trap Cards, which are Spell Speed 3.
Trap Cards may be chained to Spell Cards, other Trap Cards, or to the effects of Effect Monsters.
Normal Trap Cards are Spell Speed 2. They can be activated during either player's turn as long as it wasn't set that turn. The effects of certain Normal Trap Cards behave like Equip Cards, but the card is still considered a Normal Trap Card.
Continuous Trap Cards are also Spell Speed 2. Their effects are applied as long as they are face-up on the field.
Counter Trap Cards are a Spell Speed 3. Only other Counter Trap Cards can be chained to a Counter Trap Card.
In Turbo Duels during the Yu-Gi-Oh! 5D's anime, because the use of non-Speed Spell Spell Cards is restricted, duelists generally have a higher amount of Trap Cards in their Decks.
There are some exceptions on activating Trap Cards, some cards allow Trap Cards to be activated during the turn it's set or even from the hand.