ZED tickets are probably the most common. It stands for Zonal employee discount and is based on a pre-determined mileage between city pairs. For example LAX-SFO would be one of the lowest mileage zones and have a pretty low fare while LAX-DXB would be a higher mileage and therefore a higher fare. Each zone has a low, medium, and high category. Employees and immediate family seem to pay the medium fare and I see often that employee parents pay the high fare. There’s usually a coach category of fares and then a separate table for business class fares for airlines that have business class agreements. All the ZED stuff is usually governed by airlines via the ZED MIBA forum.

ID90 generally stands for industry discount where an ID90 is a 90% discount off a specific fare. ID75 would be a 75% discount. ID fares are much less common.

Some airlines just do a flat rate for OAL standbys. Spirit and Allegiant ring a bell where a NRSA from another airline can purchase standby travel for $25+ tax regardless of mileage.