All HTML tags look like those in the examples above. These pieces of information are called attributes. Attributes define additional characteristics of a tag. Some have predefined values, or only one possible value, whereas you can define the values of others. As we saw in our first example, HTML start tags have corresponding end tags.
End tags close a section of markup.
Some end tags are not often used because it is clear by the next tag that the previous tag has ended. In practice, it is best to insert the begin and end tags in all cases, unless you are using an HTML markup tool to enter tags, in which case it is often not practical and too time consuming. However, both capital and lowercase make valid HTML tags. Another type of HTML markup is the character entity. Character entities are markup which indicates that a special character should be inserted where the entity occurs in the document.