Hilary washes her sheets every day. (Good grief, Hilary, don't you have anything better to do with your time?)
Hilary washes herself every day. (For which we can all be grateful.)
Hilary is doing the same thing in both cases - that is, washing - but the second example is a bit odd, because the person who washes (Hilary) is the same as the person who is being washed.
That makes washes (in the second example, though not in the top one) a reflexive verb.
Reflexive verbs are easy to spot in English because of the itself/herself/himself/yourself/yourselves/myself/themselves that usually goes after the verb. Many other languages have a similar extra word or ending put in to make it clear that the person who is being washed, loved, etc is the same as the person who is doing the washing, loving.
Having said that, there are important differences in how people think of their actions. Take the rather irritating Hilary, for example. There's nothing wrong with saying that Hilary washes herself every day, but an English person would generally say Hilary washes every day, and the fact that she's washing herself would be understood without actually having to say so.
The French language, for instance, is much keener to use reflexive verb structures than English is, and this probably explains the much-treasured postcard my daughter once received from a French pen-friend after a trip to London, explaining how interesting it had been to go to Buckingham Palace and see the guards relieve themselves.
I'm beating myself up for not having gone with her to see them myself.
Thing To Use Today: a reflexive verb. There are lots of these all over the place, so help yourselves. The word reflexive comes from the Latin reflexus, bent back, from reflectere, to reflect.