What is this character called? |?

It's next to the backslash, or maybe the forward slash (above the enter key), maybe someone could shed some light onto which slash is which too...

That is called a 'pipe' key character.

It is generally used with windows DOS and linux shell commands for specifying additional parameters to the commands.

For example in dos we can do
c:\>type abc.txt|more
which displays the contains of the file one page at a time

In order to identify which slash is which, just check the head and the foot of the slash. If the head is forward than foot then its called forward slash i.e. '/'. If the head of the slash is backward than the foot then its called a backward slash i.e. '\'

Roshan N's answer is good. I just want to explain something more about the pipe character. His description of what it does works, but it isn't quite accurate. The pipe character 'pipes' the output from one command into the data used for another command. So instead of displaying the results from the first command on the screen, it sends the results to the second command. It is a way of saying "Do command A first, and with the results from command A, do command B. For example, from a command prompt, the command "systeminfo" will print a lot of information about your computer to the screen. At the command prompt, the "find" command will search for a specified string of characters or words in data that is inputed to the command. By typing the command 'systeminfo | find "Up Time"' at the command prompt, all of the data retrieved from systeminfo is piped into the input data for the find command. That command looks through all the data for the phrase "Up Time" and will only print that one line to the screen.