It is an algorithmic pattern that involves creating a 'window' over a subset of an array or string, and sliding it across the data to perform calculations efficiently.

Nested loops recalculate overlapping data repeatedly, causing O(N*K) time complexity. Sliding window maintains the state and only calculates the changes, achieving O(N).

Problems involving contiguous subarrays or substrings, such as finding the max sum of K elements, or the longest substring without repeating characters.