The elements you have created so far have appeared on new lines but some elements go inside lines of text to alter them a bit.
Save your existing page (textonly.html) as textemphasis.html. Paste this in under the final paragraph but before the closing /body tag:
<h2>Some words are bigger</h2> <p>That was a heading but this time it wasn't quite as big as the first one.</p> <h2>This is another second-level heading</h2> <p>This is the final paragraph.</p>
Indent the new lines appropriately.
Bold and strong
Find the word big in the third paragraph. Around the word put two new tags:
Save and view in a browser. Bold tags change the appearance of the text. Now put these tags are the word final in the last paragraph:
Save and view and it will probably look the same as bold. Strong is supposed to be used to show where text is more important and you also want it bold. Bold is supposed to change the appearance but not suggest any special importance. That may sound weird but there are reasons for it.
Italic and emphasis
Pick two other words and wrap one in italic tags and one in emphasis tags:
Again i is to change appearance but em changes the appearance and suggests it is more important. See what I did there?
Your page should now look something like this: