HTML Entities
Reserved characters in HTML must be replaced with entities:

< (less than) = &lt;
> (greater than) = &gt;
HTML Character Entities
Some characters are reserved in HTML.

If you use the less than (<) or greater than (>) signs in your HTML text, the browser might mix them with tags.

Entity names or entity numbers can be used to display reserved HTML characters.

Entity names look like this:

&entity_name;
Entity numbers look like this:

&#entity_number;
To display a less than sign (<) we must write: &lt; or &#60;

Entity names are easier to remember than entity numbers.

Non-breaking Space
A commonly used HTML entity is the non-breaking space: &nbsp;

A non-breaking space is a space that will not break into a new line.

Two words separated by a non-breaking space will stick together (not break into a new line). This is handy when breaking the words might be disruptive.

Examples:

§ 10
10 km/h
10 PM
Another common use of the non-breaking space is to prevent browsers from truncating spaces in HTML pages.

If you write 10 spaces in your text, the browser will remove 9 of them. To add real spaces to your text, you can use the &nbsp; character entity.