a) used to say you are not interested in something:
Make-up, who needs it?
b) used to say that someone or something is actually very important to you:
Kids? Who needs them!
GRAMMAR GRAMMAR Verb patternsYou can say that you need to do something• I need to clean (NOT I need clean) the house.If someone else is going to do something for you, you can say that you need something done or need something doing• I need my car fixed urgently. • You need your head examining!When you are talking about the object that is going to have something done to it, you can say that it needs something doing or needs something to be done• My hair needs cutting. • That box needs to be moved (NOT needs moved).NegativesYou can say that you don't need to do something or needn't do something• I don't need to leave (NOT don't need leave) until 10.• You needn't apologize (NOT needn't to apologize).!! need not means that it is not necessary to do something. Do not use it to mean must not(=are not allowed to)• You needn't take any money. • You mustn't take any sharp objects on the plane.!! needn't have means that it was not necessary for someone to do something that they in fact did. Do not use it to mean didn't need to or didn't have to (= something was not necessary)• We needn't have ordered so much food. • I didn't need OR didn't have to tell him who I was - he already knew.Noun patternsThe most common noun patterns are a need for something and a need to do something• her need for friendship • a need to preserve the environment!! Say there is a need, not 'it is a need'. Say a need for, not 'a need of'• There is a desperate need for cash.You can also use the expression be in need ofsomething• We are in need of funds (NOT We have a need of funds).
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.