The kilometre is a unit of length and is a multiple of the metre; an SI derived unit. It has the symbol km.
A kilometre is equal to 1000m, 1094 yards and 0.621 miles.
Kilometres is used to measure road distances in the US, though the UK is still using the imperial "sister" miles.
The rod is a unit of length in the imperial and US sytem and uses the symbol rod.
A rod (or perch, pole, lug) is equal to 16.5 feet or 5.5 yards.
It is a building surveyor's tool for measuring distance and is particularly useful as multiples of this unit can make up an exact acre. A perfect acre is a rectangle with edges 660 feet and 66 feet - which is 40 rods by 4 rods; i.e. 1 acre = 160 square rods.