Below text is from binomial queues article.
Although both leftist and skew heaps support merging, insertion, and delete_min all effectively in O(log n) time per operation, there is room for improvement because we know that binary heaps support insertion in constant average time per operation. Binomial queues support all three operations in O(log n) worst-case time per operation, but insertions take constant time on average.
In above text what does author mean by constant average time per operation? and how it is different from for binomial queues insertion takes constant time on average?
What is difference between constant average time per operation and constant time on average?