2D animation stands for the two-dimensional animation, meaning that characters and backgrounds in this kind of projects are created in the two-dimensional, flat space. 2D animation objects possess only the characteristics of width and height (no thickness) and are either drawn by hand or created on the computers. Another technique for 2D animation images creation is that of photographing still objects and then creating the sequence of frames.
All original 2D animation was done by hand, with animators drawing each frame or cel. After all cels are completed, the sequence is edited and screened at the speed of 24 cels per second. This speed creates the illusion of movement natural for the human eye. Before the advent of computer-generated images and 3D technology, all cartoons and animated movies were produced in this way, while computer software now enables the generation of 2D images on a computer and their further manipulation for the animation effect.
While 3D animation is much more popular nowadays, the modern animation industry still applies 2D animation techniques to make 3D objects dynamic and realistic. Therefore, even with the advent of more innovative 3D animation, 2D is here to stay without the risk of becoming obsolete.