I posted a question regarding the "deploy" feature and nobody seemed to answer it. Ok, I'll post again.

How does deploy feature work? in my case, with the resin-3.0.x.

It creates the deploy folder inside the resin, and it copies all the files into it. But my resin.conf doesn't say anything regarding the deploy folder, so how come it reads it and serves it?

What post are you referring to? After checking your other Resing posts you posted follow ups to both of them saying you got it working.

Besides that this question is a resin question, you are asking why resing picks up the extra web app, I have absolutely no idea. In Tomcat this is done when you have "auto deploy" turned on.