Question

What differences are there between a FIR filter and an IIR filter?

Answer 1

FIR(Finite Impulse Response) does not have feedback therefore it only depend on present and past input values. While IIR(Infinite Impulse Response), contain feedback hence it depends on present, past input as well ab past output. All the difference as shown in table below,

Difference between Fir and IIR filter

Characteristics	FIR	IIR
Feedback	No feedback from output side	feedback is taken from output side
Phase Response	Linear phase Response	Non Linear phase Response
Realization	can be realized using Recursive structure as well as non recursive structure	it can be realized using Recursive structure.
Stability	it is always stable	it may or may not be stable.
Memory	Need finite memory	infinite memory is required
Analog history	It has no relationship with Analog filter	Can be realized from Analog filter
Accuracy	Less accurate	Better accuracy than FIR

Note-please find me in comment box if you find any difficulty. As difference is required, I summerize it in table. Good luck