Not exactly. During a sprint (A set period of time, but constant, ie 2 weeks always), you work on something from start to finish (lets make this button show a pie graph with blah blah balh), dev to test to documentation and whatever else. Pre-sprint grooming is essentially refining tasks that are yet to be done to ensure they can be done in a sprint, or ensuring you know how much of a sprint the task will take up. You might for example break down the previous "press a button, get a pie graph" into "press a button and get a pie graph with constant values" and "make the pie graph actually retrieve our current values" (Not the greatest example, but whatever.)
Of course, this all depends who you talk to...
