BizTalk Server is an enterprise application and integration tool that enables one to connect disparate systems, applications together to one central location.
It is primarily used when you want to achieve a handshake between two separate technologies, for example : .net and SAP(though it can be used for many more technologies!). Also, its versatility is what makes it tick.
In order to facilitate data processing, BizTalk has certain adapters, which in turn, contain pipelines.
Yes, you can use it with Visual Studio 2005.