Your Evasion Class (EC) is: 10 + Body. The Body can however, can be limited by your armor type.
This is basically a creature's passive dodge.
As creatures can roll Attack Rolls (melee weapon, ranged weapon, melee spell, ranged spell), any Attack Roll that is less than the EC is considered a miss, or where the character evades or dodges the attack entirely.
Any attack roll greater than or equal to the EC is a hit.