Type C (or Europlug) is a two-wire plug that has two round pins. It fits into any socket that accepts 4.0 – 4.8 mm round contacts on 19 mm centres.
Type D has three large round pins in a triangular pattern.
Type E has two 4.8 mm round pins spaced 19 mm apart and a hole for the socket's male earthing pin.
Type F (also known as a Schuko plug) has two 4.8 mm round pins spaced 19 mm apart.