What is the meaning of 2d in getContext method?

Answer 1

'2d' stand for 'two dimensions': to get a planar context, say a standard bitmap output context...
Others context types could be handled (less often: '2d' is the mostly used), noticely 3dimensionnal 'webgl' types:

https://developer.mozilla.org/fr/docs/Web/API/HTMLCanvasElement/getContext

Answer 2

Can we use more dimensions?