Both functions invoke an interpolation from PSF data.
value() calculate only one point.
sample() resamples data with fixed step regarding independent variable.
Our dear friend Pancho sometimes makes impression to be harsh, but reading posts of some users, I can admire Pancho patience and will to responding.
Question about difference between two functions in the tool is a question like "I am too lazy to click help button and read basic information".
Cadence Virtuoso contains comprehensive and really user friendly documentation and help browser.
So, please don't behave like a rude kid. More humbleness, please.
Calm down and read this friendly 20 years old article. Article which I remember as a basic requirements to start using internet forum, irc channel and other places where people interacts.
sample() is (typically) used to sample a waveform at a different rate. You can specify a starting point, an ending point, type of sampling (linear vs log) and the interval between samples.
value is used to get the value of a waveform at a single value or multiple periodic values and each axis can be interpolated in a different way for WREAL signals. It does not have the clipping function of the sample() function. Sample() would be a very handy way to downsample part of a signal, for example.