As stated above it is a skip to next line HTML code but to be more exact HTML uses abbreviated words and symbols for it’s execution. < starts the command, "br" is short for break, "/" is an end command and > closes the command. For example < and b and> starts a command to set the typeface in bold and < and / and b and > ends it so that any words between these commands will be bold typeface. All of this is invisible to the reader as you would see with the word bold. In order for this to work HTML has to be enabled wherever you are typing. Some places use a modified version of HTML that uses brackets [ ] instead.

It is HTML code for “skip down one line”. Like pushing the enter key on your keyboard.

Need proof? Have a look at your question title. Where it used to say that code line, it now jumps down to the next line. Congratulations, you just used the HTML programming language! lol