The Fermi Level is defined as the highest occupied molecular orbital in the valence band at 0 K, so that there are many states available to accept electrons, if the case were a metal. It should be noted that this is not the case in insulators and semiconductors since the valence and conscution bands are separated. Therefore the Fermi-Level is located in the band gap. It can be seen in the diagram below. The probability of the occupation of an energy level is based on the Fermi function, but this will not be discussed at length at this level.