  We study the ``effective string picture'' of confinement, deriving
theoretical predictions for the interquark potential at finite temperature. At
low temperatures, the leading string correction to the linear confining
potential between a heavy quark-antiquark pair is the "L\"uscher term''.
Assuming a Nambu-Goto effective string action, subleading contributions can be
worked out in an analytical way. We also discuss the contribution given by a
possible ``boundary term'' in the effective action, and compare these
predictions with high precision results from simulations of lattice Z(2) gauge
theory in three dimensions, obtained with an algorithm that exploits the
duality of the Z(2) gauge model with the Ising spin model.
