They are the same only thing is that one is call the IEEE 802.1Q and the other Q in Q, however they both provide the same kind of feature.
Information About Q-in-Q Tunnels
A Q-in-Q VLAN tunnel enables a service provider to segregate the traffic of different customers in their infrastructure, while still giving the customer a full range of VLANs for their internal use by adding a second 802.1Q tag to an already tagged frame
Understanding 802.1Q Tunneling
802.1Q tunneling enables service providers to use a single VLAN to support customers who have multiple VLANs, while preserving customer VLAN IDs and keeping traffic in different customer VLANs segregated.