If you're reading this on an iPad, make sure you tell it "happy birthday." Apple CEO Steve Jobs originally introduced the world to the iPad on Jan. 27, 2010. That was five years ago, and the device has evolved from being described as a "giant iPhone" to a truly innovative gadget that changed the market and introduced millions to the power of a tablet.

Originally, most outlets thought that the gadget was a fad, something that wouldn't stick around or have any real historical substance. Gizmodo bashed the device and declared it to be terrible. However, the sales numbers disagreed. A million iPads were sold half the time it took to sell a million units of the first iPhone, according to Yahoo!. Within two to three years,  the "smart tablet" became a normal device in business, schools and the government.

When Apple released the iPad Mini, the 7.9-inch device's sales blew up and quickly exceeded sales of the 9.7-inch tablet, according to Computer World. The next rendition of the device (Apple iPad Air) sold less than previous versions, according to Wired.

The iPad is still the No. 1 tablet on the market. While other Android clones have tried to take on Apple's sales numbers, none of them have been able to exceed the iPad's sales numbers. This is probably because, as PC Magazine noted, the Android OS is not a good system for designing tablet-sized apps.

Now we're in a weird place where tablet sales are going down, but the device is still developing. However, we're reaching a point where the iPad exists in this weird space between the iPhone and Mac, where it's uncertain where the device should go design-wise, as Wired noted. But wherever it goes, Apple's userbase will follow.

So, happy birthday iPad! Here's hoping you'll have five more. (Hope you don't get too thin.)