Each companion contains a unique digital spirit, with its own personality and set of traits. As you spend time training your companion, its personality will develop. Some spirits are shy, others are gregarious, some are playful, others like to sleep, some are obedient, some are rebellious.
By interacting with and training your companion its personality will develop over time, potentially increasing its value to yourself or others.
Companion spirits are not embodied by default, and you can always choose to house your spirit in a new body. When a spirit is transferred to a new body it retains its personality, experience and traits.