In the right-hand bar, you have the Match History and Active Contracts, as well as options around related Records, Tags, Third Party Extensions, Permissions, and the Change Log.
Active Contracts are generated automatically when the Contact has an active Contract on a Listing.
Related Properties allows you to track Properties that are somehow related to the Contact. For example, this may be Properties that the Contact is a current or past owner of, or a current or past tenant of.
Related Contacts allows you to track Contacts who are somehow related to the Contact. For example, this may be the Contact's Spouse/Partner or Parent.
You can apply any of your Mailing Lists to the Contact.
You can set who has access to the record from this section. You can also change privileges and the record owner.
View Change Log
The change log shows any changes that have been made to the Listing record. From here, you can also access changes that have been made to the Property record.