What does MFE stand for?

What does MFE stand for? In The frequency of the MFE structure in the ensemble is 35.19 %. Also I found a cool page in Wikipedia http://en.wikipedia.org/wiki/List_of_…

Minimum Free Energy. This is identical to the structure and energy that Eterna shows in “natural” mode. The usefulness of MFE frequency is that often there are alternate structures possible that have free energies that are very competitive with the MFE (i.e. within a few kcal/mol). For example, the NUPACK algorithm tries to widen the gap between the MFE and the misfolds as much as possible.