They are shown in the table below:
me - to me (singular)
te - to you (singular)
le - to you, to him, to her (singular)
nos - to us (plural)
os - to you guys (plural)
les - to you all, to them (plural)
They precede conjugated verbs Siempre me llamó a esta hora. You always called me at this time.
They can connect to infinitives No tuvo que decirle la verdad. You didn't have to tell him/her the truth.
No le tuvo que decir la verdad. You didn't have to tell him/her the truth.
Pablo me compró una bicicleta. Paul bought me a bicycle. Paul bought a bicycle for me.
Pablo te compró una bicicleta. Paul bought you a bicycle. Paul bought a bicycle for you.
Pablo le compró una bicicleta. Paul bought him (her, you) a bicycle. Paul bought a bicycle for him (her, you).
Pablo nos compró una bicicleta. Paul bought us a bicycle. Paul bought a bicycle for us.
Pablo os compró una bicicleta. Paul bought you guys a bicycle. Paul bought a bicycle for you guys.
Pablo les compró una bicicleta. Paul bought them (you all) a bicycle. Paul bought a bicycle for them (you all).
Ella le llama a Juan. le = him (Juan)
Ella le llama a su hermana. le = her (hermana)
Ella le llama a usted. le = you (usted)
Ella les llama a sus padres. les = them (padres)
Ella les llama a ustedes. les = you all (ustedes)