What is the difference between a sequence and series?

Hint: A sequence is a list of objects in which repetitions are permitted and order is essential. It has members, much like a set. The length of the sequence is defined by the number of elements.
A sequence is a representation of the process of adding infinitely many quantities to a given starting quantity one after the other.

Complete answer:
One of the most fundamental topics of Arithmetic is sequence and series. A sequence is an itemised set of elements that allows for some kind of duplication, while a series is the total or the sum of all elements. One of the most famous examples of sequence and series is an arithmetic progression.
The difference between a sequence and series are as follows:


Note:
A sequence's series is the sum of the sequence's terms up to a certain number. It is sometimes abbreviated or written as Sn. The sum of a series is generally represented by the Greek capital sigma.
So, let us take a sequence $5,10,15,20,...$
Here the sum to 4 terms will be ${S_4} = 5 + 10 + 15 + 20$.