You can put elements inside other elements too — this is called nesting. If we
wanted to state that our cat is very grumpy, we could wrap the word "very" in a
<strong> element, which means that the word is to be strongly emphasized.
<p>My cat is <strong>very</strong> grumpy.</p>
You do however need to make sure that your elements are properly nested: in the example above, we opened the p element first, then the strong element, therefore we have to close the strong element first, then the p. The following is incorrect:
<p>My cat is <strong>very grumpy.</p></strong>
The elements have to open and close correctly, so they are clearly inside or outside one another. If they overlap like above, then your web browser will try to make a best guess at what you were trying to say, and you may well get unexpected results. So don't do it!