Eve Question - when and who can I can attack and where?

[Noxis]

Simple questions really (from a Eve noob).

What are the restrictions on aggressive actions?

Obviously anything in 0.0 goes, but what about 0.1 + ?

Also can you attack wanted people anywhere without fear of a sent gun taking you down?

Is there also a linked guide anyone knows of for all the icons that can appear next to someone as to what they mean?

 

[Noxis]

If you attack anyone in 0.5+ then you can expect to be reduced to not very much at all pretty damn quickly, unless you're at war with your target

In 0.4 - 0.1 you can attack people and Concord won't come to their aid, but expect to be shot at by sentries if ther are any nearby.

What distance do I need to be from sent guns before I can be aggressive?