parlare

Here's how to conjugate 'parlare' (to speak) in the present tense:
Io parlo (I speak)
Tu parli (You speak - singular, informal)
Lui/Lei parla (He/She speaks)
Noi parliamo (We speak)
Voi parlate (You speak - plural, informal)
Loro parlano (They speak)

While both mean 'to speak' or 'to say', 'parlare' generally means 'to speak' in the sense of making sounds with your mouth or having a conversation. 'Dire' means 'to say' or 'to tell' a specific piece of information.
Example: Parlo italiano. (I speak Italian.)
Example: Dico la verità. (I tell the truth.)

You'll often use 'parlare' with prepositions like 'con' (with), 'di' (about), or 'a' (to).
Example: Parlo con Maria. (I speak with Maria.)
Example: Parlo di politica. (I speak about politics.)
Example: Parlo a te. (I speak to you.)

Yes, 'parlare' is commonly used to mean 'to talk'. There's no real distinction between 'to speak' and 'to talk' in Italian with this verb.
Example: Non parlare ad alta voce. (Don't talk loudly.)

To form the passato prossimo, you use the auxiliary verb 'avere' (to have) and the past participle 'parlato'.
Example: Ho parlato con lui. (I have spoken with him.)

A common expression is 'parlare a vanvera', which means 'to speak nonsense' or 'to talk out of turn'.
Example: Non parlare a vanvera! (Don't talk nonsense!)

Parlo is a regular -are verb, which means its conjugations follow a predictable pattern. This makes it easier to learn!

You would say: Posso parlare italiano. (I can speak Italian.) 'Potere' (to be able to/can) is the verb you need here.

The imperative form (commands) for 'parlare' is:
Parla! (Speak! - singular, informal)
Parli! (Speak! - singular, formal)
Parliamo! (Let's speak!)
Parlate! (Speak! - plural, informal)

Absolutely! It's the most common verb to use when discussing what languages you speak.
Example: Parlo inglese e italiano. (I speak English and Italian.)