#### Answer

a)
A sequence is an ordered list of numbers and a series is the sum of a list of number.
b)
A convergent series is a series where the sum of all of its terms is finite. A divergent series is a series where the sum of all of its terms is infinite or its $n$-th partial sum doesn't approach a finite number as $nā \infty$.

#### Work Step by Step

a)
Definition of sequence and series.
b)
Definition of convergent and divergent series.