An HTML element is defined by a starting tag. If the element contains other content, it ends with a closing tag, where the element name is preceded by a forward slash as shown below with few tags:-
There are some HTML elements which don’t need to be closed, such as <img…/>, <hr /> and <br /> elements. These are known as void elements.
HTML elements with no content are called empty elements. Empty elements do not have an end tag, such as the <br> element (which indicates a line break).
Nested HTML Elements:-
It is very much allowed to keep one HTML element inside another HTML element.HTML elements can be nested (elements can contain elements).
The <html> element defines the whole document.
It has a start tag <html> and an end tag </html>.
Inside the <html> element is the <body> element.
The <body> element defines the document body.
It has a start tag <body> and an end tag </body>.
Inside the <body> element is two other HTML elements: <h1> and <p>.
The <h1> element defines a heading.
It has a start tag <h1> and an end tag </h1>.
The element content is “BCIS Notes”.
The <p> element defines a paragraph.
It has a start tag <p> and an end tag </p>.
The element content is” This page provides notes of each subject”.
Do Not Forget the End Tag
Some HTML elements will display correctly, even if you forget the end tag:
The example above works in all browsers, because the closing tag is considered optional.
Never rely on this. It might produce unexpected results and/or errors if you forget the end tag.
Empty HTML Elements:-
HTML elements with no content are called empty elements. <br> is an empty element without a closing tag (the <br> tag defines a line break):
Empty elements can be “closed” in the opening tag like this: <br />.
HTML Is Not Case Sensitive:-
HTML tags are not case sensitive: <p> means the same as <p>.The HTML5 standard does not require lowercase tags, but W3C recommends lowercase in HTML and demands lowercase for stricter document types like XHTML.