A Booster Pack (ブースターパック Būsutā Pakku) is a pack of Yu-Gi-Oh! cards from one of the Booster Sets. OCG Booster Packs contain around 5 cards each, whereas TCG packs contain 9 cards. Each pack is guaranteed a Rare.
In the TCG, there is a 1:5 chance to get a Super Rare. In current sets there is a 1:12 chance to get an Ultra Rare, or in some older sets, there is a 1:24 chance to get an Ultra Rare. To get a Secret Rare, there is a 1:23 or a 1:31 odd.
Booster Packs can be bought at most game stores and at some general/department stores.