Active Guard is done by holding the Guard button and leaving the joystick neutral to guard high or mid attacks. Or Active Guard Low by holding the Guard button and then holding the joystick down. Active Guard protects against all types of attacks including staggers and rapid succession attacks. Here you see the same Sophitia attack safely guarded using Active Guard. The next areas you will need to understand are the hit ranges.
High attacks can be block standing or ducked by crouching.
High attacks tend to be horizontal attacks and are usually great for hitting opponents using lateral movements. High attacks can be blocked standing or ducked. This means the attack hits in a mid range region. Mid attacks must be blocked standing and can not be avoided by crouching. Most mid attacks are vertical attacks and thus easy to evade with lateral movements.