Mainly speaking, there are only four hand positions widely used in Tai Ji Quan, three are depicted below, the hook, fist and tai ji palm. The fourth would only be used while wielding a jien or double edge sword often called a tai ji sword.
Parts of the Fist: 1. Back, 2. Face, 3. Heart, 4. Eye, 5. Heel.
Parts of the Tai Chi Palm: 1. Back, 2. Heart, 3. Tip, 4. Edge.
Parts of the Hook: 1. Back, 2. Face, 3. Heart, 4. Tip.