Number of people infected by 1 infectious person. The R is a calculated number. It is updated every Tuesday and Friday. The R is 2 weeks old, because a reliable calculation of the reproduction number can only be made after 14 days.
The reproduction number (R) indicates how fast the coronavirus is spreading. R shows how many people on average are infected by someone who carries the virus. The number of transmissions is more or less constant when R is 1, drops when R is below 1 and increases when R is higher than 1.