A sequence is a number pattern in a definite order following a certain rule.
It can be denoted by: a1, a2, a3, a4, a5 ..........an-1, an
Series is a sum of terms in a sequence.
It can be denoted by: a1 + a2 + a3 + a4 + a5 ..........an-1 + an
Series/Sequence are of two types: arithmetic and geometric.
Sequences and series can be finite or infinite. A finite sequence/series is one that eventually comes to an end. Infinite sequences/series are those that continue indefinitely.