Hi Deepak,
WBT courses are objects that are published via the LSO Authoring Environment and played on the portal. They are time- and location-independent, so the learner can take them at their leisure. You can purchase SCORM-compliant WBTs from vendors and convert, import and publish, or create your own using the Authoring Environment.
Virtual Learning Rooms are time-dependent, but location-independent courses hosted by an instructor. Learners log into the VLR at the start time of the course, and the instructor presents the material to them via Adobe Connect Pro VLR.
These are two separate delivery methods in SAP LSO, independent of each other.
Hope this helps,
Connie