A dictionary or associative array data type is a collection of unique key-value pairs so they do not duplicate.
The collections mentioned earlier, namely, lists and tuples, are ordered and store elements in the order we add them. Dictionaries are different. They do not remember the order in which we add items, and instead, store items so that operations on the dictionary contents are as efficient as possible:
Strictly speaking, as of Python 3.7, the internal structure of dictionaries has changed: as of this version, dictionaries remember the order in which we added keys. However, we do not need to tie logic to this property-lists are better for storing the order of things.
Lists and tuples are indexed. It means the position of each element is a number — an ordinal number from the beginning of the collection. Dictionary keys do not have to be numbers. They can be many other types of data, most often strings. There are no specific patterns between the dictionary keys except for the uniqueness guarantee, when the indexes of the list and the tuple are consistent with no omissions, and the increment between elements is one.