buildings with no plans: these are vacant, pending sale, or for some other reason unlikely to be used much without substantial rehabilitation.
buildings with plans: these have some plans, but have active or likely zoning cases left to overcome first
buildings with zoning entitlement: these have plans and are cleared of all zoning hurdles (either getting approval or being a by-right project to start with); a lot of buildings go on sale at this point to a buyer who plans to do the construction, so a building may end up parked in this state for a while; there may substantial details and room for public input/benefit as part of public space permitting and/or public financing circumstances
under construction: these are buildings that have actively began construction
recently constructed: new buildings, probably good to go for a while
preservation areas: areas where buildings should be deterred for environmental or other reasons