This is a great resource for anybody that isn't formally trained in computer science. A lot of programmers use an abstract data type like a dictionary or hash table, but many of the self-taught and even some formally trained treat it like a magical black box that stores key-value entries very efficiently. What a hash table/dictionary gives it near O(1) properties is a good hashing function for the key, and having a good distribution of buckets for all the keys when collisions occur.

I think a lot of programmers have good understanding of many data structures. But I think hashes and dictionaries are still taken for granted. What they really need to think of hashes as many magical black boxes and the hashing function directs which key to go to which magical bucket. :)