A list is a data structure designed to store ordered sets of elements.
In this case, the word "ordered" means we store the structural elements in the order in which we added them.
Items in the list are indexed, meaning they have a number that tells you their position. The numbering always starts from zero and is always monotonous. It means that each subsequent item index increases by one — this numbering is also called continuous numbering. If you delete items at the beginning or middle of the list or insert items in the middle, Python recalculates the indexes and preserves the above numbering properties.