Simple bash scritpting question

[Black666]

I've read a bash scripting tutorial and now I read various scripts and try to understand what they are doing.
What I've seen many times and don't really know what it does is something like this:

# Source function library.
. /etc/rc.d/init.d/functions
# Source networking configuration.
. /etc/sysconfig/network

Ok, "functions" and "network" are scripts that are executed here - but what is the ". " for? Why not just "/etc/rc.d/init.d/functions" instead of ". /etc/rc.d/init.d/functions"

[andrzej]

"." = source command

Pasted from 'man bash' (I think words "in the current shell environment" are the key here):

. filename [arguments]
source filename [arguments]
Read and execute commands from filename in the cur-
rent shell environment and return the exit status
of the last command executed from filename. If
filename does not contain a slash, file names in
PATH are used to find the directory containing
filename. The file searched for in PATH need not
be executable. When bash is not in posix mode, the
current directory is searched if no file is found
in PATH. If the sourcepath option to the shopt
builtin command is turned off, the PATH is not
searched. If any arguments are supplied, they
become the positional parameters when filename is
executed. Otherwise the positional parameters are
unchanged. The return status is the status of the
last command exited within the script (0 if no com-
mands are executed), and false if filename is not
found or cannot be read.

[Feztaa]

If the script defines an alias, variable, or function (which is what they do, in this case), then those aliases, variables, and functions will be lost after the script exits if the '.' is not present. The '.' allows those aliases, variables, and functions to be inserted into the "current shell environment" for use by the script later on.