I'll is a contracted form of 'I will' (or 'I shall' in some dialects), functioning as a pronoun+auxiliary verb contraction in English. In speech, it's a single, unstressed syllable typically realized as /aɪl/ in connected speech. It marks future intention and is extremely common in everyday conversation, with pronunciation that emphasizes the /aɪ/ nucleus and a light /l/ at the end, often blending with following sounds.
Full pronunciation guide
