A Two is avoiding 'I am unloved, unwanted', and the compensating strategy is to become the person others need first — you know what someone wants before they do, and you supply it. The type belongs to the heart centre (Two, Three, Four), whose undertone is shame and concern with image; a Two's image is 'the good one, the reliable one, the needed one'.
The key point in the mechanism: a Two's giving keeps a ledger, only nobody reads it, the Two included. Hence the classic loop — give and give, never ask, accumulate expectation, watch it go unmet, then explode or fall ill.
Where you'll recognise it: refusing is hard, you're acutely aware of others' needs and oddly numb to your own, and being overlooked wounds you more than most. Running well, a Two is the warmest person in the room: genuinely sees people, genuinely cares for them, makes a relationship feel safe just by being in it. Stuck, giving becomes control — 'after everything I've done for you'. Under stress the line runs to Eight (suddenly hard, calling in the debt); in growth it runs to Four (admitting you have needs and a dark side too). For a Two, 'I want' is the hardest sentence and the most healing one.