Headers are paired tags. You can create entire web pages with headers and marked-up text. It would be boring, however. Headers may have font definitions and color as well. This is an unordered list and this line is incorrectly placed unless you are making a comment for the entire list.
Lists can help make a page read and look better.
But it will look different on different browsers or even on different hardware with the same browser. Long entries will wraparound just like you would expect them to so that they look like a related line of text. Long entries don't have as much white space but it is a neat way to block text. This is an ordered list and this line is incorrectly placed. Lists can help make a page read and look better.