the extent to which time or effort is well used for the intended task or purpose
Efficiency in general describes the extent to which time or effort is well used for the intended task or purpose. It is often used with the specific purpose of relaying the capability of a specific application of effort to produce a specific outcome effectively with a minimum amount or quantity of waste, expense, or unnecessary effort.
Questions having the efficiency tag regards users possibility to be efficient completing task, or more general efficiency.
Reference: http://en.wikipedia.org/wiki/Efficiency
