[quote=@Guilty Spark]
<Snipped quote by Mag Lev>

How are they used, practically speaking. Tattoos, inscribed on items/weapons?
[/quote]

Some use tattoos, some inscribe them on weapons or items. For example, a Journeyman could inscribe a light rune on a rock and toss it, activate it and produce a small burst of light. The items generally place the effect on the object while the tattoos allow you to direct the effect to another surface.