#1 Transit VLAN (or subnet) would have traffic crossing it that's not to or from any end user hosts on the VLAN (or subnet). For instance, might be traffic between two L3 devices that both have an interface on the VLAN (or subnet).
#2 Activates WRED using IP precedence markings. (If you're unfamilar with RED and/or WRED, much information can be found on the subject both on Cisco's web site or searching the Internet.)
#3 Count of packets that were to be transmitted out the interface but were discarded (dropped) for some reason instead.
