How are Solution, Sol and suspension different to each other? Give two examples for each

Example: Return the Cartesian product of this RDD and another one, that is, the RDD of all pairs of elements (a, b) where a is in self and b is in other.

rdd = sc.parallelize([1, 2])
sorted(rdd.cartesian(rdd).collect())
# [(1, 1), (1, 2), (2, 1), (2, 2)]