The speed of light in vacuum is 300,000,000 meter per second.
So, since the answers so far are conflicting…
Yes and no. It depends on how you’re looking at it.
Photons move at one speed and one speed only: c.
However, when moving through a medium, photons wind up being absorbed by atoms along the way and being re-emitted. There is a slight delay when this happens between the time that the photon is absorbed and when it is re-emitted. This delay is predictable, so that the overall effect is as if the light were being slowed down.
For an analogy, consider a hypothetical car which can only go 20 mph. Because it can only go 20 mph, any time you need to stop, the car is destroyed, and once you finish what you need to do, a new one is created around you, already going 20 mph (there’s a lot of padding involved).
Now, that car only ever goes 20 mph… but the average speed across your journey will be something less than 20 mph, depending on how often you have to stop for stop lights, bathroom breaks, and so forth, and how long those take.
That’s the same situation that occurs with light going through a medium. An individual photon never moves at anything other than c, but due to photons being absorbed and re-emitted, and a delay happening each time, the “front” of the beam of light moves at something slower than c.
So, in optics, where we’re concerned with the overall “beam” of light, we say that the light is moving more slowly, as a shorthand way of talking about things, just like you might say, “Well, the speed limit is 70, but let’s assume our average speed will be 60” when planning a long trip.