Responses to a 'weak Two'
there are 4 types of rebid after a 'weak two':
A simple raise shows 3 or 4-card support and approximately 6-13 points (insufficient values for a game contract). It is preemptive and completely non-forcing.
A jump raise Usually shows a weak, preemptive hand (with 4-card support) or 5 cards and almost nothing. But it may also be made by a strong hand that believes game will make.
A new suit
Natural and round forcing, it shows at least a 5-card suit and denies support for partner's suit.... However, some pairs prefer to play a new suit as natural and non forcing..
2NT
Strong, artificial forcing bid. Opener is asked to show a feature in a side suit, i.e. an ace or king, by bidding that suit at the three level. The objective being to assess if a game is makeable and to choose a suit or NT contract.