What do Parallel and Sequential mean under "Agent Test Type"?

Depending on the number of agent locations used, you may want to generate synthetic measurements a couple different ways.

Parallel will run one measurement, at the requested frequency, from EVERY location you have selected.
Example - 3 locations selected at a 15 minute frequency set to parallel will run 12 measurements over the course of an hour.

Sequential will run ONE measurement from ONE location you have selected (random choice of what you have selected) at the requested frequency.
Example - 3 locations selected at a 15 minute frequency set to sequential will run 4 measurements over the course of an hour.