An actual email I sent today:
leggings are sort of between tights and jeans. they are more coverage (in terms of opacity) and they allow you to wear a greater range of footwear (i.e. sandals). It's important to distinguish between leggings (which have a heavy fabric weight and often will have side seams, think the kind of stretch pants you'd wear to the gym) and footless tights (which are, um, footless tights) when making a pants/no pants decision.Sometimes I don't even know who I am.