Timeline: This is a chart bar used to express the relative time between a single timing segment and other timing segments in the same request.
View the color scheme.
Caption: This is the name of timing segment.
Started: This is the offset in seconds from the start of the current request.
Duration: This is the duration in seconds and percentage of the timing segment in the current request.
See also:
Group Level Timeline Charts
Webpage Timing (Only in Add-on)