"lib" Prefix on Libraries
You can name a library whatever you want, but if you want gcc's -l flag to find the right one, you need to name it the way that link describes. For example:
gcc -o myapp myapp.c -lmWill compile myapp.c, link the resulting object with libm.a, and output an executable called myapp. These days, there might be a more complicated search path involving dynamic library names, etc., but you should get the basic idea from this example.
From the gcc man page:
-llibrary ...... surrounds library with
liband.aand searches several directories.