what is the difference between をand で used with the verb 話す?

is there a different if i say
日本語で話す
and if i say
日本語を話す

my book gave me both of this particle with the verb hanasu but didn't explain the difference

Question

what is the difference between をand で used with the verb 話す?

is there a different if i say
日本語で話す
and if i say
日本語を話す

my book gave me both of this particle with the verb hanasu but didn't explain the difference

Answer

私は、日本語を話します。＝I speak Japanese.

私は、日本語で話します。＝I speak in Japanese.

Answer

日本語で話す
Parlare in giapponese.

日本語を話す
Parlare il giapponese.