Streaming Replication

Hi,
I am new to PG Streaming Replication and I have a simple question hopefully
someone can answer this easily.

I setup a Primary Hot Standby and they are connecting each other without
problem.
Looking at the wal sender process, both servers pointing to the same
location as follow:

Primary:
postgres 3018 0.0 0.1 203888 3024 ? Ss 19:25 0:00 postgres:
wal sender process postgres 10.89.94.31(43169) streaming 0/D913018

Standby:
postgres 3645 0.0 0.1 212556 3096 ? Ss 19:25 0:00 postgres:
wal receiver process streaming 0/D913018

My question is when looking at the standby processes, I see startup process
as follow:

postgres 3320 0.0 0.0 203048 2084 ? Ss 18:11 0:00 postgres:
startup process recovering 00000001000000000000000D

What is that suppose to mean?
Is it really recovering some data from WAL record in the pg_xlog folder?

Thanks~
Ning