Hola Anshu

A direct object pronoun is a pronoun that refers to a direct object. For example: Yo compro un regalo = yo lo compro. (I buy it), Ella hace los deberes = Ella los hace (She does them) 

An indirect object pronoun is a pronoun that refers to an indirect object. For example: Yo compré un regalo a mi madre = Yo le compré un regalo (I bought her a present), Él dijo unas palabras a sus hijos = Él les dijo unas palabras (He said some words to them) 

Generally you ask the verb "what/who?" and that gives you the direct object and you ask the verb "for whom, to whom?" and that gives you the indirect object. 

Here is a bit of information about these pronouns:

direct object pronouns

indirect object pronouns

I hope it helps

Saludos