This is a “forward slash”: /. Notice the top of it leans forward.
This is a “backslash”: \. Notice the way the top leans back.
How do you know when to use a / or a \?
Forward slashes tell your computer you're looking for something external to your system, like web pages. Example: http://nwls.wislib.org/Tech/index.htm
Backslashes tell your computer you're looking for something inside your system, like a drive or a file. Example: C:\WINDOWS\system32\browser.dll