From BlenderWiki

Soft body object type

Physical object, deforms on collision.

Actor

This causes the physics engine to evaluate your object, causing your object to be seen as more than part of the world (a simple wall or floor). This object can now be seen by other active objects.

At this point your object is not affected by normal physics (e.g. gravity) but is seen as more than just a background object. This is useful for interaction between objects that need not have physics properties, such as gravity, e.g. a button on a wall.

Ghost

Ghost gives the object the ability to pass through other objects. This helps save processing time while calculating objects’ physics (e.g. bouncing, friction, etc.). A collision with another object is still detected and reported to your game logic.

Invisible

If the object is set to "Invisible", it isn't rendered in the Game Engine.

Advanced

Collision advanced settings.

Mass

Mass affects the amount of force that is required to move an object. The greater the mass the greater the force that need to be applied to the object in order to move the object. Mass will not cause objects to fall faster or slower. To slow an object down use dampening, if you wish to accelerate the falling rate increase gravity (normal gravity is 9.81).

Shape match

Enables softbody shape matching goal

Bending Const

Enables bending contraints

LinStiff

Linear stiffness of the softbody links

Friction

Dynamic friction

kMT

Shape matching threshold

Bounds

The Blender Game Engine has a number of ways of dealing with the shapes of objects. The reason that the game engine avoids highly accurate, per face object collisions, is due to the high level of processing power that it would demand. It is often faster, during game play, to uses a simpler system such as a box or a sphere for an object that’s shape is very similar.

The bounds are calculated from the object’s centre, which is designated by the pink dot normally at the centre of your object. It is not uncommon or useful to move this centre to a more convenient location. This can be done in the Editing context (F9) and choosing one of the 3 options that focus around Centre movement (see Mesh for more info).

Convex Hull and static Triangle Mesh are designed for uses with World objects floors, walls, trees, etc.

Blender has no generic way of interacting with hollow objects. An example, which would be difficult to create, would be a cup to shake dice in.