State anxiety is the anxiety you are feeling now, in response to a fear or danger of a particular object or situation. Trait anxiety is the general level of anxiety you have as a result of your personality and how you handle and cope with stressors.
So state anxiety requires treatment that is focused on the particular object or situation causing the anxiety (e.g CBT), while trait anxiety requires a broad treatment approach (e.g. relaxation techniques, exercise, natural supplements).