i was sorta wondering what a 'wave' looks like in 3d

what got me thinking was i know my microwave oven's door has a screen
such that the holes are supposed to me smaller than the microwave itself
so it dosn't leave the area

but i wasn't sure how to think of the wave itself was it a narrow beam
sorta like a pencil that had the length =freq i am guessing not or if
ever it turned onto it's profile then it would go thru the screen
apature so do i assume it's length and width are always same? in x y z

or even out of a directional microwave emitter is it immediately like a
doughnut always sorta propagating

all the books i have always show waves like a pencil line and sorta
describe it 2d