The quote is not really in philosophy, so you might also want to ask in a sociology or psychology SE question. But I wrote my PhD dissertation on selfhood.
I see in this quotation three concepts:
(1) The self as a socially constituted entity. A self is created in a context populated by significant "others" at different historical periods in the life of a person. The idea here is that to be a self (here meaning the sort of entity that has self-consciousness) is to be built on certain constituting relationships to others. In other words to be a self is to receive certain ideas and thought processes from others (i.e., one's society).
(2) The self's identity as the self's unity. it has a single identity who partakes through life and is influenced--and exerts influence. This is to say that the self is a unified node that operates in relation to other nodes in the social matrix.
(3) Identity as a complex notion. And while we talk about our identity as if it is a unit, in effect we can unwrap the latent identities that have formed through out lives. Here, the point is that social identity theory and several contemporary philosophical views of the self point out that the identity of the self varies by social context. In other words, sometimes my configuration is a college professor, some times as a white guy (esp. in Japan), sometimes as a man. And these notions of identity don't always overlap; rather different identities matter in different interactive contexts.
I don't know if that made things any clearer for you but that's what I see happening in that quote. There's a lot to unpack there.
