It represents a duration which is basically difference between dates. It can also be used for datetime manipulations.
EXAMPLE:
i = datetime.datetime(2000, 3,  11,  7, 45,  23)
j = datetime.datetime( 2019,  6, 8, 2, 45, 13)
k = j - i
print(type(k))
print("k =", k)
OUTPUT:
<class 'datetime.timedelta'>
k = 7027 days, 18:59:50