Wood with Smooth Texture

Question

Note: I do not have much experience with woodworking.

How is that wood can have a smooth texture with multiple "rings"? (I heard that trees the same number of concentric circle as their "age")

So how do producers make it wood so that it does not only have concentric circles, but smooth continous ones?

Image of the side of desk (the darkened top is just a shadow, the white is a piece of metal - I do not know why it is there):

I have taken a closer look with my eye (not on the image, but the physical desk) and do not see any discontinuities (no visible straight lines where multiple boards could be connected / glued together)

Answer 1

Plywood and veneer are products manufactured in a manner which results in continuous grain lines such as those shown in the photo.

Picture a cylinder of a tree trunk and apply a strong straight cutting edge to the cylinder in the same axis of the trunk. The cutting edge will create a continuous panel of thin wood until the tree trunk becomes too small to handle the forces applied by the cutter.

One could postulate that with a large enough panel and small enough tree diameter, the rings could be traced and patterned in such a way that you could see where each layer began and ended the "overlap" but such practice seems rather obsessive.

The full process is somewhat more complex than the description above. Here's an image from a website which provides a more detailed description.