'Here' refers to the location(s) that the card occupies. For most cards, such as minions and artifacts, that means one location. For example, Fey Changeling. For auras, that usually means 4 locations, most commonly the surface of 4 sites. For example, A Midsummer Night's Dream. Another example is the use of 'here' on Evil Presence, which includes the site surfaces but could also include void squares as well, if the aura occupied a void square. When a site itself uses the word 'here,' that includes both the site's surface location and it's subsurface location. For example, Dome of Osiros protects minions in its subsurface as well as surface. 'Here' is analogous to 'there.'