Heuristic evaluation is a method to evaluate the usability of a user interface.
It is generally advantageous in the initial stages of a design project because it does not require user testing because it’s performed by an expert. Most heuristic evaluations can be done within a few days, depending on the complexity of the project.
The heuristic evaluation can also be performed before a redesign, in order to identify the most problematic areas of a system and focus the development on functional aspects.
The heuristics published in “Usability Engineering” by Jakob Nielsen in 1994 are probably the most widely used.
Here is the original article by Nielsen: Ten Usability Heuristics