The word “drone” has taken on a few different meanings over the years. Some people think of a drone as a bee, others might think of those predator drones that the military uses. The drones that most people talk about today are simply radio controlled aircraft that have some level of autonomous features. A drone can be a plane, a helicopter, a quadcopter, or any combination in-between. Most of the drones sold today are quadcopters. They have 4 rotors and a flight controller that is used to stabilize the lift from the each propeller.

For example, OPTI has a built-in Optiflow Sensor (a downward facing sensor), which functions by picking out the patterns on the ground to ensure that the drone maintains a straight position.  ATTI, conversely, works a bit differently. With the ATTI, the drone employs other techniques apart from the external sensors to keep the drone in the right orientation and altitude. Thus, the drone can hover in place, or drift slightly around with the wind serving as a push. You will also find a GPS in some drones, and they help the drone to maintain coordinated and precise flights and landings.
HD video starts at the resolution of 1080p as a minimum. For all of these drones, the video is captured at the lower resolution of 720p, even when they claim to have HD cameras. The resolution of still images is always higher than the video. With still photos, the resolution can be as low as 1 megapixel (equal to 1000p) and that resolution is considered HD for still photos. 
The Altair AA108 is durably built and will not break easily. You can count on a solid flight time of around 10 minutes, a bit less when you’re running it FPV. However the 720p camera really works well and connects to your phone through WiFi. It’s easy to fly because it has 3 flight modes, 1 beginner, 2 intermediate and 3 advanced mode. It also has Altitude Hold which allows you to take your thumb off the control and the drone holds it’s own altitude, making it very stable because it’s not bouncing up and down as you try to maintain altitude!