what is 3D modelling?
3D modelling is when you make a three dimensional model sing software on the computer. 3D modelling is used to design cars to making bridges. It is useful to many companys and can save them a lot of money in some cases, however it can be a hard thing to become good at.
when is it used in anime?
3D modelling is used quite a bit in anime now and is used to design characters and then later on program them. A very common use of this is when making videos for the vocaloid Hatsune Miku, It is normally used for miku miku dance and project diva.