Timsort is a sorting algorithm that is efficient for real-world data and not created in an academic laboratory. Tim Peters created Timsort for the Python programming language in 2001. Timsort first analyses the list it is trying to sort and then chooses an approach based on the analysis of the list.
Timsort’s big O notation is O(n log n). To learn about Big O notation, read this.
Source: Timsort — the fastest sorting algorithm you’ve never heard of, an article by Brandon Skerritt.