First Steps.

Hello,

Taking first steps in the security world.
I know that a 'firewall' is nothing but a configuration file for iptables,
but that's about it.
I need recommendations for literature or other sources of reliable knowledge
that start off with answers to questions such as: 'What is a port?'

Any time and trouble appreciated.
Regards,

Weaver.
-- 

Religion is regarded by the common people as true,
by the wise as false,
and by the rulers as useful.

— Lucius Annæus Seneca.

Terrorism, the new religion.