Each hexagram consists of two trigrams which are groups of three lines. The lower trigram also designates the inside and the upper trigram also designates the outside.
For each trigram I give its title in Richard Wilhelm's book translated by Cary F. Baynes.
The trigrams are described in detail in Wilhelm's translation of the eighth wing also called Shuo Kua.
You will also find information on Wikipedia in the article titled as Ba gua.
The eight trigrams are:
Eternity
Richard Wilhelm / Cary F. Baynes: Ch'ien, the Creative, Heaven
Material
Richard Wilhelm / Cary F. Baynes: K'un, the Receptive, Earth
Rule
Richard Wilhelm / Cary F. Baynes: Chen, the Arousing, Thunder
Question or Answer
Richard Wilhelm / Cary F. Baynes: Sun, the Gentle, Wind
Sending or Receiving
Richard Wilhelm / Cary F. Baynes: Li, the Clinging, Flame
Hygiene
Richard Wilhelm / Cary F. Baynes: K'an the abysmal, Water
Restraint
Richard Wilhelm / Cary F. Baynes: Ken, Keeping Still, Mountain
Overflow
Richard Wilhelm / Cary F. Baynes: Tui, the Joyous, Lake