One of the reasons that video slots became so popular is that the physical reels on the slot machines could only hold a realistic maximum of 22 or so symbols on them before they became too big to work on a mechanical level. With a video slot, which is computer-driven, you can theoretically have 40, 60, or even 100 symbols on each virtual reel, which changes the odds dramatically and enables you to offer much larger jackpots than you would be able to otherwise.
But as far as online goes, yeah, they’re all video slots, it’s just that some of them are set up to act like the old mechanical slots with 3 reels and 20 or so symbols per reel.
Here’s some more interesting slot machine trivia for anyone who’s interested: the reason that fruit became the symbol of choice on slot machines in the earlier part of the century is because it became illegal to pay out cash at one point. So they modified the slot machines so that you could win fruit-flavored candies. The “bar” symbols that you see on a traditional slot machine reel are actually a corruption of a symbol for prizes of sticks of gum.