Probably a better description is that Erlang's raison d'etre is -fault tolerant- applications. Concurrency and distribution are just natural results of prioritizing that (because to isolate faults you need strong concurrency primitives, lest some number of bad behaving processes prevent others from being able to succeed, and you also need distribution, lest hardware faults lead to system failure). But, yeah, there are lots of good links attached.

For what it means for concurrency, it's not intended to be a high performant number crunching system, but rather one built to to make concurrency safe (which ends up being extremely performant for I/O bound workloads, and extremely predictable for CPU bound ones) - M:N threading model, immutable data, shared almost nothing, achieved via the actor model.