Here are all headings (<h1>, <h2>, <h3>, <h4>, <h5> en <h6>) underneath each other:
This is <h1> (Head 1). The biggest possible heading.
This is <h2> (Head 2).
This is <h3> (Head 3).
This is <h4> (Head 4).
This is <h5> (Head 5).
This is <h6> (Head 6). The smallest possible heading.