How to distinguish sequences from collections in programming?

In programming, sequences and collections are different types of data structures, although they sometimes overlap.

• Sequence is an ordered set of elements that can be accessed by index. The order of elements is important. Examples: lists, arrays, strings.

• Collection is a more general concept that includes any data structures that store a set of elements. Collections can be ordered or unordered, can contain unique elements or duplicates.

For example, in Java:

• Sequences: List, Queue
• Collections: Set, Map, List

The main difference is that sequences have order and index-based access, while collections may not have order, and access can be by key or through iteration.

Example:

• List (sequence): ["a", "b", "c"] — elements are ordered and accessible by index.
• Set (collection): {"a", "b", "c"} — order is not guaranteed, duplicates are not allowed.