This is a screenshot from a Cisco book. It says that 2 VLANs can be bridged using some L2 device also. As far as I know it is possible only by using some L3 device. Can someone please explain it how 2 VLANs can be bridged using a L2 device?
A bridge / L2 device forwards frames based on the destination MAC address. Most often this is a common switch. If you bridge two VLANs they become a single L2 broadcast domain. Normally you wouldn't want that.
A router / L3 device forwards packets based on the destination IP address. If you use it to connect two VLANs they can communicate across the router (on L3/IP) but stay separate L2 broadcast domains.
Simply put, if you bridge two VLANs together, they effectively become one VLAN.
There will no longer be a distinction between the VLANs -- they will act as one. For example a broadcast will be forwarded to all ports on both VLANs. Flooding will span both VLANs