Temporal energy was a type of energy sometimes released from the contact of two versions of the same item or individual coming from different time ages.
When the Fourth Doctor met the Eighth Doctor and attempted to enter the Master's TARDIS, they touched their sonic screwdrivers together, creating enough temporal energy to get inside. (AUDIO: The Light at the End)
When the Master's TARDIS sustained damage from a crash on Gardezza, it began leaking vast amounts of temporal energy, resulting in time distortion. This affected chronometres and the process of ageing in the vicinity of the crashed timeship. (AUDIO: Beneath the Viscoid)