Psychological activities can also be thought of as those where the primary focus is on the execution of some psychological manipulation.
Below is a list of a few of the more common ones:
Physical activities don't directly manipulate the state of mind of a bottom or submissive. Instead they provide sensations and stimuli which the bottom or submissive can use and interpret to reach a certain state of mind themselves.
Psychological activities, on the other hand, are intended to have an immediate and direct impact on the state of mind or feelings of a slave, submissive or bottom. They are overt and direct attempts to create or manipulate feelings, thoughts, emotions, sense of identity and awareness. Thus, potentially, they provide an opportunity to directly reach desired psychological outcomes without going through all that pesky physical effort some other BDSM activities require.