What is the point of semi-transparent stain?

[Wade Lippman]

I am staining the supports on my deck; the deck itself is PVC. I am using the semi-transparent stain the original owner left behind.

It is really thin and doesn't cover very well; I am tempted to put on a second coat.

So:
1) Is there some advantage to semi-transparent over solid; or paint for that matter?
There must be some advantage or it wouldn't exist; but it is not obvious what that advantage is.
2) I may not have enough to finish. Can I get solid stain to finish up in the same color? (it is a custom color, but the formula is on the can). Would they look okay near (not right next) to each other?
3) Can I put a second coat of stain on, or is that not recommended?

thanks.

[Brad Adams]

It lets the grain show, while still protecting the wood.

[Wayne Lomman]

Wade, in wood finishing terms, stain is always transparent to some degree. As Brad said, it allows the grain to be visible. I assume that the product is designed to be a finish in itself. Often these products require regular to up. They are thin so that they are absorbed into the timber. Check the instructions but usually you can put on as many coats as you like. Just observe recommended drying times between coats. In Australia we have to apply more coats than the northern hemisphere as we don't have the high levels of atmospheric pollution to block uv. Cheers