No need to put yourself down! Everyone has to start somewhere.
So a normal animation usually runs one animation frame per system frame. So the speed is dependent on your system frame, or fps.
By using Sprite.AnimationVariable+60*dt, your animation will progress at 60 frames per second regardless of what your system fps is. If your fps is lower than 60, some frames will be skipped. Or you can use 10*dt for 10 frames a second.
The problem is that you can only set a whole number as an animation frame, like frame 1, 2, or 3. You cannot have a frame 3.248. The dt expression will start giving you fractional numbers. So to get past this we use either floor(), which means round down, and ceil() (ceiling), which rounds up. Floor(3.5) = 3, ceil(3.5) = 4.
This gives us a new problem though - if I just use the animation frame and add to it, it might keep rounding down, preventing the animation from progressing! For example, I'm on frame 2, and dt adds .9 on tick. This 2.9 gets rounded down to 2. Next tick, I add .7 - this 2.7 also gets rounded down to 2.
This is why we need a separate variable to keep track of our progress. As in the previous example, If I stored the 2.9 in a variable, this tick would show animation frame 2, then next tick I add .7 to 2.9 resulting in 3.6, this would show frame 3.
Sprite.AnimationFrameCount gives you how many frames an animation is, lets say 13. Normally, it would progress from 0, 1, 2, and so on until 13. Then instead of 14, which doesn't exist, it would go back to 0. Now we have the same problem as above when using dt - we get decimals instead of whole numbers. If we progress from 13.7 to 14.5, we want to carry over that .5 when we go back to the beginning. You can do this with modulo. 14.5%14=0.5
So basically the loop event I described as above goes like this:
If my current AnimationVariable (14.5) is greater than AnimationFrameCount+1 (14. I didn't have +1 above but should have since we're rounding down), set AnimationVariable to 0 + whatever is leftover after 14 (14.5%14=0.5). Then of course we would need to round down to set the actual animation frame which is 0. But the next tick would continue adding from 0.5.
This is a bit past beginner territory, so don't be discouraged if you don't get it. Good luck with your project!