Extraversion describes a person's usual social role: To what extent you tend to dominate the social room, your need for social interaction, and your usual level of energy.
People on one extreme are assertive, sociable, and energetic, while people on the other extreme are accommodative, solitary, and low-key.
Assertiveness is a facet that concerns your 'weight' when interacting with others. To what extent are you the person who leads conversations or group activities? The scale goes from Accommodative to Assertive. People who are Accommodative let others take the lead and keep their opinions to themselves. People who are Assertive take charge and make their opinions heard.
Sociability concerns your need for social interaction with others. How much do you enjoy spending time among other people? The scale goes from Solitary to Sociable. People who are Solitary like to be alone and can be perceived as quiet or socially withdrawn. People who are Sociable like to be among other people and can be perceived as socially outgoing.
Energy level is a narrow facet in Extraversion. It covers your activity level and intensity in interaction with others. The scale goes from Low-key to Energetic. People who are Low-key like low-energy environments and can give a restrained appearance. People who are Energetic enjoy high-energy environments and give an active and lively appearance.