The msbuild contains output tag. It has avialable attributes: TaskParameter and PropertyName, ItemName. How they can be used? What are they containing? Please, can you help me to understand and give an example? For example you can use xmlpeek task with output tag inside. (I read documentation on msdn but I still don't get it. :( )
These are a way of passing values back from the task to the MSBuild script. It is basically a way of mapping a property in the compiled task code that has been decorated with the [Output] attribute back to a property in your MSBuild file. This page gives you more details about it: MSDN: Output Element (MSBuild). This article also has a good example of it in action: How to auto-increment assembly version using a custom MSBuild task