Making a pattern can be quite easy, anything that repeats could be a pattern, such as 565656, or cat dog cat dog cat dog. To find a pattern you often need 2 full repeats of the pattern.
Sequences are ordered sets of items, which makes it possible to easily determine the next item. This term is often reserved for numbers, but it very similar to a pattern. To determine a sequence you often need at least 3 terms of the sequence or the definition.
For example, we can have a sequence starting with 2, 4, 6, and we add all 3 numbers to get the next, so the next number would be 12, i.e. 2, 4, 6, 12, 22, 40, …
Series are often confused with a sequences, but mathematically it is the sum of the sequence.