*.la and *.a

[Darren Cook <darrenj@example.com>]

What are *.la and *.a extensions?

Comparing two redhat machines the freetype rpm 1.3.1-7 has these two
extra files in /usr/lib compared to 1.3.1-5:
-rw-r--r--    1 root     root       199016 Dec 12 13:21 libttf.a
lrwxrwxrwx    1 root     root           15 Dec 12 13:32 libttf.so ->
libttf.so.2.2.0

The link I can make by hand, but I'm wondering if I need the .a file as
well? There is also a libttf.la there (on both machines). 

Darren