A unit 'enters' a location or site when it is summoned there, or when it moves there from somewhere else. 'Somewhere else' means 'a different location' for entering locations, and it means 'a different site' for entering sites. The method of movement doesn't matter; it can be any type of movement, including the Move and Attack basic ability, effects that cause a unit to 'take a step,' teleportation, or other forced movement. The relevant questions are: Was it summoned there, OR Did it move there from somewhere else? If either of those are true, then the unit 'entered' that location or site. Further notes: If a site is placed under an existing unit, the unit did not enter the site. The unit didn't move, and it wasn't just summoned, so it didn't enter. This can happen if Rubble was replaced by a site, or it was a voidwalk minion in the void and a site was played there. If a non-minion occupies a location or site and then becomes a minion without moving (e.g. Enchantress), the minion did not enter. The minion didn't move and wasn't just summoned. If a minion moves between levels of a site (e.g. surface to subsurface, or subsurface to surface), it does not enter the site, since it was already occupying the site. (It does enter the specific location of surface or subsurface.) For oversized units, they only enter a location or site if they didn't previously occupy it. For example: The Mountain Giant occupies the four left squares, and then takes a step to the east. It enters the two sites in the right column, but it does not enter the two sites in the middle column, since it already occupied those sites before the move. See the 'Oversized Units' codex entry for more details.