Follow on is a term used in the longer version of the game (Test match). It is used when a team batting second in its first innings is asked to bat again (follow on) immediately upon the completion of its innings.
The team that takes first strike has the privilege of asking itsopponents to follow on (bat again) if the opponent falls short of itsfirst innings target by 200 or more runs.
However, this is in a Test match that runs the full duration of fivedays. If the first day of a Test match gets fully wiped out (due to rain or other unforeseen circumstances) then the Test match is effectively cut down to a four-day affair. In such a circumstance 150 runs or more is the benchmark to ask a team to follow on. But for this to happen the full day has to be wiped out without a single ball being bowled. Even if one ball is bowled then the match becomes a five-day affair.
In the event of the first two/ three/ four days of the match beingcompletely washed out then the follow on target will not be reducedfurther than 150 runs.
The system of follow on is implemented in order to save time, as doing so might enable a result, which might otherwise peter into a draw for lack of time.