Discrete Wavelet Transform (DWT) is a time-frequency analysis tool for which the wavelets are discretely sampled. DWT is different from the Fourier transform, which provides frequency information on the whole time domain. A key advantage of DWT is that it provides frequency information at different time points.
Wavelet transform functions implement the Mallat algorithm (an iterate algorithm in the DWT field) and apply wavelet transform on multiple sequences simultaneously, or perform the inverse of this process.