EMOM stands for “every minute on the minute.” So, for a given length of time, you perform a specific number of reps of a movement (or movements) at the top of every new minute, then rest until the next minute starts again.
As an example, here’s a 10-minute EMOM of 5 push-ups and 10 squats: at time 0:00 on the clock, perform 5 push-ups and 10 squats, then rest the remainder of the minute. When the clock hits 1:00, perform the two movements again. Repeat 10 times. Your final round will start at the 9: 00-minute mark since your first round technically started at 0 and not 1.