Reflexive Verbs:

A verb is reflexive when the subject and the object are the same.

I wash myself.
subject: I
verb: wash
object: myself

Since the subject and object are the same, the verb is reflexive.

I wash the car.
subject: I
verb: wash
object: car

Since the subject and object are different, the verb is not reflexive.

Here's another example of how a verb can be either reflexive or non-reflexive.

I scratch myself.
subject: I
verb: scratch
object: myself

Since the subject and object are the same, the verb is reflexive.

I scratch the dog.
subject: I
verb: scratch
object: dog

Since the subject and object are different, the verb is not reflexive.

When a verb is reflexive, the infinitive ends in "se."

lavar
to wash (non-reflexive)

lavarse
to wash oneself (reflexive)

rascar
to scratch (non-reflexive)

rascarse
to scratch oneself (reflexive)

There is one reflexive verb you have been using since you began studying Spanish.

llamarse - to call oneself

¿Cómo se llama usted?
What do you call yourself?

Me llamo Juan.
I call myself Juan.

Note: A more "natural" translation would be "What is your name?" and "My name is Juan."

When you learned to conjugate regular verbs, you needed to learn a set of pronouns called "subject pronouns."

lavar

yo lavo
tú lavas
él, ella, usted lava
nosotros/as lavamos
vosotros/as laváis
ellos, ellas, ustedes lavan

To learn to conjugate reflexive verbs, you need to learn a different set of pronouns called "reflexive pronouns." These pronouns are positioned before the verb, while the ending "se" is dropped and the verb is conjugated normally.

lavarse

yo me lavo
I wash (myself)

tú te lavas
you wash (yourself) (informal)

él se lava
he washes (himself)

ella se lava
she washes (herself)

usted se lava
you wash (yourself) (formal)

nosotros nos lavamos
we wash (ourselves)

nosotras nos lavamos
we wash (ourselves) (feminine)

vosotros os laváis
you-all wash (yourselves) (informal)

vosotras os laváis
you-all wash (yourselves) (informal, feminine)

ustedes se lavan
you-all wash (yourselves)(formal)

ellos se lavan
they wash (themselves)

ellas se lavan
they wash (themselves) (feminine)

The reflexive pronouns are not subject pronouns; rather they are object pronouns.

me (myself)
te (yourself)
se (himself, herself, yourself)
nos (ourselves)
os (yourselves)
se (themselves, yourselves)

The purpose of the reflexive object pronouns is to show that the action of the verb remains with the subject.

Juan se lava la cara.
Juan washes his face. (reflexive)

Juan lava su carro. (non-reflexive)
Juan washes his car.

Note: When referring to body parts, use the definite article, thus "la cara" not "su cara."

Note that many, many verbs can be made reflexive. All it means when a verb is reflexive is that the action remains with the subject.

wash the dog (non-reflexive)
wash your face (reflexive)

raise the book (non-reflexive)
raise your arm (reflexive)

put the baby to bed (non-reflexive)
go to bed (reflexive)

wake up your son (non-reflexive)
wake up yourself (reflexive) ...and so on

lavarse to wash oneself

yo me lavo
tú te lavas
él se lava
ella se lava
usted se lava
nosotros nos lavamos
nosotras nos lavamos
vosotros os laváis
vosotras os laváis
ustedes se lavan
ellos se lavan
ellas se lavan