What does 10 x 100 on 1:00 rest mean ?

Workout sets will be listed by the number of times you will swim a certain distance (in this case 10) and the distance you will cover (in this case 100 yards/meters).  Since all workouts are based on a 25 yard/meter pool….and 1 lap will = 25 yards/meters…..when I say “100″ it refers to 100 yards/meters which equals 4 laps.   So….10 x 100 means you are to swim 4 laps / 10 times ( for a total of 40 laps or 1000 yards/meters).  The 1:00 rest means that after every 100 yards/meters (or 4 laps) you will rest for 1 minute.