This is a vocabulary for precisely describing a position in time and the passage of time itself, in both real and musical terms.
In addition to real time (e.g. seconds), two units of time are used:
frames
 and beats
.  A frame is a numbered quantum of time.  Frame
time is related to real-time by the frame rate
 or sample rate
,
time:framesPerSecond.  A beat is a single pulse of musical time.  Beat time is
related to real-time by the tempo
, time:beatsPerMinute.
Musical time additionally has a meter
 which describes passage of time
in terms of musical bars
.  A bar is a higher level grouping of beats.
The meter describes how many beats are in one bar.