Definition of Immunities
From AmtWiki
NOTE: This is an outdated rule, please see the Current Rule Book
Having an immunity does what one would expect. You can not be harmed by that specific thing.
For example, having an immunity to traps would cause you to not be effected by traps. Immunity to poison, prevents you from dying in 100 count from poison.
List of immunities (for standard classes):
Glossary definition of immunity