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.