A route of administration for a drug, examples, Actiq (fentanyl transmucosal system) and Saphris (asenapine sublingual tablets)
Buccal administration works as follows:
1) substance is introduced to the cheek/gum region
2) the substance is absorbed by the membranes
3) the substance goes into the bloodstream
Actiq, by the way, is a lollipop looking thing that delivers fentanyl to your cheek and gum membranes slowly.
Also, they taste good (about 2 grams of sugar plus flavorings per pop)