A combo station typically refers to a husband / wife or an operator / club call. It’s common practice to list COMBO in the description field for the lines being marked as such on Netlogger, so the worklist is aware of the special circumstances around their call.
When a two-person combo station checks in, such as a husband and wife, NCS needs to verbally hear both individuals during the check-in for it to be an official check-in. Additionally, each member of the combo should receive their own turn, because they may be working different awards, etc. This does not typically apply to members who combo with a club or special event callsign but can be offered at the discretion of the NCS.