To answer the second part of your question, "hybrid" means "mixed" -- so a hybrid network is a mix of what makes up a network. According to TheFreeDictionary, a hybrid network is a network that contains network hardware and equipment -- or network infrastructure (to relate back to the first term) -- from multiple vendors. In example, a network that includes Juniper Networks' switches and HP ProCurve's data center management solution would be considered a hybrid network. Some infrastructure networks only contain network equipment from one vendor -- like Cisco -- because the pieces are interoperable and would therefore avoid mis-communication between devices; it could also create a faster network (in theory). Being locked in to an expensive vendor, however, leads companies to choose the hybrid network route, because it can cost a lot less and more appropriately fit the needs of the business.
This was first published in September 2009