The period of time from the evening to the early hours of the next day.

रात का समय

English Usage: We will meet tonight at the café.

Hindi Usage: हम आज रात कैफे में मिलेंगे।

During the evening of the current day.

आज रात

English Usage: She has a performance tonight.

Hindi Usage: उसकी आज रात एक प्रस्तुति है।