It is used for specifying the headings or titles in the HTML document, It is Container Type of Tag.
align: It is used to specify the alignment of headline. Values are “left, right, center and justify’. e.g. align=”left’ (default).
<H1> Chapter l</H1>
<H4 > Chapter 4</H4>
In the above example the text within <H1> tag will be displayed in large size and it would be center aligned. There are 6 headline levels where <H1> is highest level and <H6> is the lowest level.