Sampling
The word "sampling" is used in various fields but in this area(electrical engineering), we should get some sample signal at the poing during time interval and according to the signal data, we can make the sampling data.
Sampling Theorem
If the signal is sampled every T seconds, then x(t) can be reconstructed from these samples with no distortion.
period T :sampling interval
p(t) : sampling function
$ \omega_s = \frac{2\pi}{T} : sampling frequency $
$ x_p(t) = x(t)p(t) $