What is the following cooking utensil used for? I am interested in knowing what the top pot is used for. I have a similar pot with holes at the bottom. I used this one to steam vegetables while I come something on the bottom pot. This makes sense, however the pot on the picture has no holes so I don't know how it would be used. The boiling water will not be able to pass into the top pot. What is this used for?

If this is not a good question to ask please help me make it better.
It's a double boiler. You use it when you need to use 'soft' heat. 

If you need to melt chocolate, or if you are making a hollandaise, or something that can easily scorch using direct heat, you use this pot.  It has a much more forgiving heat, the heat is generated from steam from the water that boils in the bottom pot.