The three lengths \textwidth, \linewidth and \hsize seem to all hold the width of the current line. At least I never saw some real difference between \textwidth and \linewidth in my code. Both seem to be identical even when changed, e.g. by a minipage environment.
Could someone give me an elaborate explanation of the differences between these lengths? I like to understand them in detail. I know that the first two are from LaTeX and the latter one from plainTeX.
There is also \columnwidth which seems to be identical to \linewidth or \textwidth in one-column mode, right? Except when the line is reduced by a minipage or quote etc. environment.