A pattern is a sequence of things that follows a rule. Patterns are everywhere. Artists and designers often use patterns. So do poets when they make rhymes, and musicians when they repeat a tune. Dance steps are a kind of pattern. Patterns are often found in nature, too, for example in the shape of flowers. In maths you can have patterns of numbers or patterns of shapes.
In art, weaving always follows a pattern. Symmetry is also a kind of pattern. The Fibonacci sequence is another.
It can be interesting to look for patterns. It helps you understand how things are made and why they look the way they do.