In computer terminology, vaporware is used for products that don't exist yet, despite the fact that they're already being advertised. A lot of vaporware never becomes available at all.
After you see ads for a cool new computer game, it might be months (or years) before you can buy it. In some cases, you'll never be able to buy this vaporware. Sometimes it takes so long for developers to finish a product that other companies get there first, releasing their own version and making the vaporware obsolete. Imagine a product that's announced with great fanfare and then never heard about again, as though it's vanished in a puff of vapor: hence the term vaporware.