[Coder-san]

[...]

Risking that I might sound stupid: What is a reflector and why do you have to protect your code from them?

"reflectors" would be wrong, the product's name is ".Net Reflector". It is a source-code extractor. It reflects the source code of a .NET PE, in the form of VB.Net or C# code perfectly as the very project it was made from.
There are other software similar to that like "Dis#".

The reason people prefer to protect their code is to well ... protect their code from being stolen, mis-used, etc. But I personally don't see the point unless you are that good, in which case I doubt one would use .Net application solely.

And no don't worry, asking questions is not considered stupid. Pretending you know about something with a question mark in your head is stupid.