gcc - unknown switches (absent also from the manpage)

I'm trying to experiment with shared objects and found the below snippet on http://www.gambas-it.org/wiki/index.php?title=Creare_una_Libreria_condivisa_(Shared_Library)_.so

gcc -g -shared -Wl,-soname,libprimo.so.0 -o libprimo.so.0.0 primo.o -lc

I browsed trough the manpages and online, but I didn't find what the -lc switch does, can someone tell me?