A backslash looks like this: \. A slash, also known — albeit rarely — as a slant or oblique stroke or simply stroke looks like this: /.
There are no backslashes in web addresses (technical note: okay, maybe sometimes, but so effectively never as to be never).
All of the “strokes” or “slashes” in a web address are just regular old slashes, not backslashes.
So you read something like http://www.almanac.com like this: h t t p colon slash slash w w w dot almanac dot com.
In conventional everyday normal person world, the only time you’ll have cause to use the word backslash is when you’re using the MS-DOS command line, and need to refer to a directory. In MS-DOS, directory names use the backslash. So you read C:\fred as c colon backslash fred.
When you read web addresses, though, ditch the back and embrace the slash.
Side note: newspapers, especially small local ones, have an annoying habit of reproducing web addresses with backslashes. They should stop this.