Adsense - Targeting type "social" ?

What is the new "Social" targeting type?

[BedSupperclub]

Hi,

Was using Adsense's new interface today and in the "targeting Types" report (under Performance reports) I saw the following list:

(Unmatched ad requests)

Contextual

Interest-based

Placement

Social

What is the "Social" type?

[levo]

[adsense.blogspot.com...]