Adding Standard units

Adding Standard units

when I create in my map new units, new unis are showen in custom units, but I saw in one map new units added to "standard unit" category.
How it is posible?

in standard, are always already existing units.
What you saw is probably an existing unit, but it's race and class modified, so for example, an undead standard unit is shown in the night elf screen.

Thx for help