Similar to how you would put http:// in front of a link to a web address, you can also use file:/// to specify an actual file or location available to your local machine or local network. Note the triple-slash (///) after file rather than the double-slash normally used with "http://"

Say you have a file called Test.txt available on a share named Share1 on a server named Server1. You can specify a link to it as:

file:///\\Server1\Share1\Test.txt

For a link to a file on your local machine you can also use drive letters, but note that passing this link to someone else will cause the link to point to something on their machine, not yours. Say you have a file in C:\Temp called Test.txt, the link would look like:

file:///c:\Temp\Test.txt