Sampling Theorem:
Let x(t) be a BAND-LIMITED signal with X(w) = 0 for |w| > w_m. Then x(t) is uniquely determined by its samples x(nT), n=-2,-1,0,1,2... IF w_s > 2w_m, where w_x = 2*pi/T
Given these samples, we can reconstruct x(t) through an impulse train where amplitudes are successive sample values.
THIS DEFINITION IS EXTRACTED FROM THE TEXTBOOK.
Signals & Systems Second Edition Alan V. Oppenheim, Alan S. Willsky, with S. Hamid Nawab