A suppository is a drug delivery system that is inserted into the rectum (rectal suppository), vagina (vaginal suppository) or urethra (urethral suppository), where it dissolves or melts.
They are used to deliver both systemically-acting and locally-acting medications.
The alternative term for delivery of medicine via such routes is pharmaceutical pessary.
The general principle is that the suppository is inserted as a solid, and will dissolve or melt inside the body to deliver the medicine pseudo received by the many blood vessels that follow the larger intestine. – Wiki