The tag <p> shows the starting of the paragraph and the tag </p> determines the end of a paragraph. In between these tags the content of the paragraph is written. It is recommended that we should put <p> at the beginning of the paragraph to make it easy for the reader that this is the actual material. Sometimes in HTML, we do not use the ending tag </p> after the paragraph, this is optional.
In HTML document the beginning tag is strongly recommended but the ending tag is optional. This is so because when the next paragraph begins <p> is placed and it is automatically considered to be the end of previous paragraph and the start of the next paragraph.
We can also refer it as the starting of next paragraph is the ending of the previous paragraph or starting of any other tag related to new text will refer the end of the previous paragraph, so there is no hard and fast rule to end a paragraph using the ending tag </p>.
We can end a paragraph using any other tag for example the start of an unordered list having a tag <UL> which will start the list items or elements. A paragraph cannot be kept empty for example we cannot write more than one paragraph tag in one line continuously like <p><p><p>, as this refers that the paragraph is empty.
Therefore, it will be against the rules. It should have a single break or a space. Doing this the browsers will consider your document as illegal or they will generate too many spaces or no spaces.
And if you want extra spaces or breaks, you can use the tag
<BR> which generates a line break that is leaves an empty line between the text or document. To make a logical HTML document you should write heading 1 for paragraph 1 and heading 2 for paragraph 2 and so on.