Two methods that make linear convolution look like circular convolution are overlap-save and overlap-add. The overlap-save procedure cuts the signal up into equal length segments with some overlap. Then it takes the DFT of the segments and saves the parts of the convolution that correspond to the circular convolution.

What is overlap save method used for?

overlaps the input frames by the same amount. samples of the previous frame are ``saved'' for computing the next frame.

Why overlap add method is used?

The overlap-add method is used to break long signals into smaller segments for easier processing. FFT convolution uses the overlap-add method together with the Fast Fourier Transform, allowing signals to be convolved by multiplying their frequency spectra.