Answer:
A cel is a transparent drawing sheet
Step-by-step explanation:
Traditional 2-D cel animation was a technique used before the diffusion of easier-and-faster-to-use digital alternatives.
The procedure was quite simple: the artist drew the outline of a character on one side of this transparent plastic sheet, and the coloring was done on the other side. Then, these sheets were placed on a background. Pictures of different movements were taken, and when sped up, it would seem like the character was moving.
Brian McSweeney is an Irish artist who has worked on many famous animations such as The Swan Princess, An American Tail, Spiderwick, Lord of the Rings, just to name a few.