It's true. Spam is a kind of canned meat. Spam is also the e-mail's you get that are trash. Spam is also when someone puts some junk on the internet.

"Spam" is an abbreviation of "Spiced Ham" (canned meat, viande conservée)

Spam is "massive" email that companies send you, sometimes about things you are not interested in.

In the Internet context it is junk.