You will get a much better answer from a native Spanish speaker, but from a Gringo, Quedar means to stay. . (ts a special verb having several forms: Simple, Reflexive, Special and accidental. Dejar is to leave something somewhere. Yo deje los platos en la cocina. I left the plates in the kitchen.
Quedar in the simple tense means with a permanent location, In the reflexive tense its usally a temporary situation. The special form of Quedar is used with ropas(clothes) dinero (money) and with time.