1.
~ is a spoken form of ‘had’, especially when ‘had’ is an auxiliary verb. It is added to the end of the pronoun which is the subject of the verb. For example, ‘you had’ can be shortened to ‘you’d’.
2.
~ is a spoken form of ‘would’. It is added to the end of the pronoun which is the subject of the verb. For example, ‘I would’ can be shortened to ‘I’d’.