When the offense reaches the first down line they get a new set of four downs. The order of downs goes:
Announcers describe down and distance with numbers like 1st and 10.
The first number is the current down. The second number is the distance to the first down line.
You may also hear the phrase replaced with the word goal like 4th & goal.
The offense gets a first down when they reach the first down line.
The first down line is placed ten yards away from the new line of scrimmage. If a team is within ten yards of the end zone, the goal line becomes the first down line.
A turnover on downs happens when the offense fails to reach or go beyond the first down line in four downs. The other team will get possession of the ball.