There are two kinds of lists on web pages, ordered lists and unordered lists. Ordered lists can use numbers (default, or 1), letters (A or a), or roman numbers (I or i). Unordered lists can use bullets (default, or disc), circles (circle), squares (square), or no marker (none) at all.
An ordered list starts and ends with the <ol></ol> tag.
An unordered list starts and ends with the <ul></ul> tag.
Each item in either kind of list starts and ends with the <li></li> tag.
You can nest unordered or ordered lists inside of other unordered or ordered lists.
You can start an ordered list at a number other than 1 or a letter other than A (<ol start="5">).
You can have an ordered list run in reverse (<ol reversed>).