Dont confuse custom POI's with regular POI's and waypoints.
The City Navigator map software is loaded with a bizillion (ok maybe 6 million :rolleyes
regular POI's like lodging, campgrounds, restaurants, stores, bars, post offices ect... They are all on the 2610 when you load the maps.
Every Garmin GPS that can run City Nav will have these regular POI's once the maps are loaded.
Custom POI's are ones that folks have created and share for things like speed traps, specific motorcycle dealers, or their favorite restaurant chain. Some of these may already be in the regular POI data base.
On units that support these you can load thousands (maybe millions?) of these.
With speed traps the unit will alert you when you are near them.
Neat stuff, but not a necessity for me.
Waypoints are points that you define either by marking them as you travel or using the map (either on the unit or PC).
Pretty much every GPS makes waypoints, but the number can be limited to 500 or so that the unit can handle.