When looking up and selecting a contact file in the Sales module within the Sales Channel context, besides the name of the contact a series of little symbols can appear. This is what they stand for:
Membership: You'll be able to see a snapshot of which one just by sliding the mouse over the symbol.
The contact currently has a marketing offer, a.k.a. an advantage assigned to them. You can see these in the general tab of the information menu of the contact file, in the marketing alerts section.
Note: When one or more notes are created within a contact file, this symbol will be displayed next to the name when a contact search is made from the sales menus in the Sales Channel context.
Credit balance: This is the amount of money the contact has available to spend in your institution. For example: When an event is cancelled, contacts can be directly refunded on their credit cards, but if that was not possible, contacts would have the amount of money of the cancelled event available for future purchases within your institution.
Pending account allowed: This is the amount that your institution allows a contact to pay with some delay. For example: When a school buys tickets for its students to go to a museum, they don't usually pay on the spot. The pending account allows the school to pay after the visit of the students.