Indirect object nouns and pronouns (i pronomi indiretti) answer the question to whom? or for whom? In English, the word "to" is sometimes omitted:

We gave a cookbook to Uncle John.

We gave Uncle John a cookbook.

In Italian, the preposition a is always used before an indirect object noun:

Ho regalato un libro di cucina allo zio Giovanni. (I gave a cookbook to Uncle John.)

Perché non regali un profumo alla mamma? (Why don't you give Mother some perfume?)

Puoi spiegare questa ricetta a Paolo? (Can you explain this recipe to Paul?)

Indirect object pronouns replace indirect object nouns. They are identical in form to direct object pronouns, except for the third-person forms gli, le, and loro. For all the forms, see below.

ITALIAN INDIRECT OBJECT PRONOUNS
 
PERSON
 SINGULAR
 PLURAL
 
I
 mi (to/for me)
 ci (to/for us)
 
II
 ti (to/for you, informal)
 vi (to/for you, informal)
 
III
 lo, la (to, for him/her)
 li, le (to/for them, masculine/feminine)
 

 La (to/for you, formal)
 Li, Le (to/for you, formal, masculine/feminine)
 

All indirect object pronouns except loro and Loro precede a conjugated verb, just like the direct object pronouns (loro and Loro follow the verb):

Le ho dato tre ricette. (I gave her three recipes.)

Ci offrono un caffè. (They offer us a cup of coffee.)

Parliamo loro domani. (We'll talk to them tomorrow.)

Similarly, indirect object pronouns attach to infinitives, which lose their final -e:

Non ho tempo di parlargli. (I have no time to talk to him.)

If the infinitive is preceded by a conjugated form of dovere, potere, or volere, the indirect object pronoun may also precede the conjugated verb:

Voglio parlargli./Gli voglio parlare. (I want to talk to him.)

Also note that le and gli are never elided before a verb beginning with a vowel or an h:

Le offro un caffè. (I offer her a cup of coffee.)

Gli hanno detto "Ciao!". (They said "Ciao!" to him.)

The table below provides a few common Italian verbs that are often used with indirect object nouns or pronouns.

VERBS THAT TAKE ON INDIRECT OBJECTS
 
dare
 to give
 
dire
 to say
 
domandare
 to ask
 
(im)prestare
 to lend
 
insegnare
 to teach
 
mandare
 to send
 
mostrare
 to show
 
offrire
 to offer
 
portare
 to bring
 
preparare
 to prepare
 
regalare
 to give (as a gift)
 
rendere
 to return, give back
 
riportare
 to bring back
 
scrivere
 to write
 
telefonare
 to telephone