From Shoryuken Wiki, Marvel vs. Capcom 3 Strategy and More!

Contents 1 Hit Boxes 1.1 Hurt Box 1.2 Attack Box 1.3 Physical Extent

Hit Boxes

As a 2-D fighting game, Skullgirls characters interact with each other based on a system of overlapping hit boxes in the game's engine. The hit boxes appear and disappear with set timings measurable by Frames. Attack boxes appear during the active portions of an attack, and will hit if they overlap with any of an opponent's vulnerable hurt boxes. Hit boxes are invisible during normal gameplay but can be seen through an option in the Practice Room.

The startup, active, and recovery frames for Filia's c.MP. Hurt boxes and Filia's physical extent appear in all frames. Attack boxes appear only in the active frames.

Hurt Box

Hurt Boxes represent the vulnerable body of the character. Hair, weapons, and other inactive extremities do not have hurt boxes. Hands, feet, and limbs usually have vulnerable hurt boxes even when attacking.

Attack Box

Attack boxes appear during the active frames of attacks, representing the hand, foot, limb, or weapon the character uses in the attack. Attack boxes often overlap with the characters vulnerable hurt boxes.

Physical Extent

The physical extent hit box represents the center of the character on screen and does not interact with attack or hurt boxes. Characters cannot overlap physical extents and will attempt to push each other out of the way when their physical extents collide.