what is O(N^2) in bubble sort method

#include <stdio.h>

void swap(int xp, int yp) {
    int temp = *xp;
    xp = yp;
    *yp = temp;
}

void bubbleSort(int arr[], int n) {
    for (int i = 0; i < n-1; i++) {
        for (int j = 0; j < n-i-1; j++) {
            if (arr[j] > arr[j+1]) {
                swap(&arr[j], &arr[j+1]);
            }
        }
    }
}

int main() {
    int arr[] = {64, 25, 12, 22, 11};
    int n = sizeof(arr)/sizeof(arr[0]);

    bubbleSort(arr, n);

    printf("Sorted array: \n");
    for (int i=0; i < n; i++)
        printf("%d ", arr[i]);

    return 0;
}