What is the meaning of 'light is a wave'?

Question

Do they mean "light moves in wave and not in a straight line'.?

Answer 1

they mean that light is an electromagnetic wave - like a radio wave except at a much higher frequency. (more specifically, light can be described mathematically as a wave - it can also be described as a particle (a photon))

The light you see has a wavelength of between 400 and 700 nanometres. The wave nature of light can be shown with the classic two slit experiment which shows a diffraction pattern
think of light as a wave like ripples on the surface of a pond after a pebble is dropped in it.
from a point source a long way away (a star for example), the light expands out in circles - but to an observer far away, the wave font will appear to be flat as the diameter is a long way away.

Answer 2

light can be described as a traveling wave, if you stand still, and if somehow you were able to look at just one slice of a light wave moving past you, you would see its "wave" going up and coming down, similar to looking at a floating wood in the ocean, you see the wood moving up and down, but not really moving forward or backward.

However the energy is being trasmitted in the wave, by the wave, since the wave is traveling. The direction of travel is in a straight line, for the most part. You can think of it as a surfer riding a big wave all the way to shore, energy of light travels along with the wave.

So light is a wave, and does travel as a wave(which isn't a straight line), but the wave as a whole travels in a straight line.

Answer 3

This gets into quantum theory, which I am just starting to study, but light moves in transverse waves if I remember right... which means they move like "~~~~~" waves if you know what i mean and they move like sound waves at the same time... which is a sort of slinky-ish movement. so they move in a ~~~~ fashion and a straight line fashion simultaneously. Crazy isn't it? Light is weird.