The subject is the person or the thing doing the action of the verb. The object is the person or the thing receiving it.
Juan compra una manzana (an apple). Subject: Juan. Object: una manzana.
Laura ama a Juan. Subject: Laura. Object: Juan.
Toco el piano. Subject: Yo (implied). Object: el piano.
María llama a Jorge. Subject: María. Object: Jorge.
