Smart goals are a mnemonic believed to originated with Doran, Miller, & Cunninghamare.  Smart goals are smart because they are:

S. Specific

Contrast: If goals are unspecific, then they are also likely to be unmeasurable and therefore not time oriented or attainable.

M. Measurable

Contrast: If goals are unmeasurable, how can anyone determine whether or not any progress has been made?

A. Attainable

Contrast: If goals are unattainable, why bother trying to achieve something that cannot be accomplished?

R. Relevant

Contrast: If goals are irrelevant, they will likely not be very valuable to your overall purpose or vision.

T. Time-bound

Contrast: If goals are not bound by time or schedule, then they will never become a matter of urgency.