Prolog is a declarative programming language which employs mathematical logic and its inference mechanism to represent knowledge in specific domains and reason with it.
Its name comes from the contraction of "PROgramming in LOGic".
Its theoretical model is SL-resolution.

Obligatory reading ! Two autobiographical texts on the genesis of the language and logic programming as a new discipline:

• The early history of Logic Programming
  by Robert Kowalski (CACM, vol.31:1, 1988).
• The birth of Prolog
  by Alain Colmerauer and Philippe Roussel (for the 20th birthday of Prolog, in 1992).

---