This page describes interpolation basics with figures and example,mention matlab command for interpolation.
Interpolation is the process which increases the sampling rate of the signal. Hence it is also called Up sampling. This is done by inserting samples with some consideration between samples.
Interpolation exampleX (n) = [0 2 4 6 8], at Fs sample rate
D=2, sampling factor
Y (n) = [0 1 2 3 4 5 6 7 8], at Fs X D sample rate