Springs can be classified into four categories based on their force-bearing properties:

1. Compression spring: Stores energy when compressed, used in shock absorbers, ballpoint pens, etc.

2. Tension spring: Generates elasticity when stretched, commonly found in fitness equipment, garage doors. 

3. Torsion Spring: Resists torsional motion, such as in clothespins and hinges. 

4. Bent Spring: Resists bending force, less frequently used

By shape classification:

1. Spiral spring (cylindrical shape is the most common, including compression/extension/twisting types)

2. Leaf spring: used in vehicle suspension systems

3. Butterfly spring: multi-layered ring structure, used in high-load scenarios 4. Coiled Spring: Flat metal strips are wound to form a spring, used in clockwork toys and clocks.

Other special types:

1. Nitrogen spring: Utilizes gas compression and is used in the mold industry.

2. Constant force spring: Provides a constant output force, used in tape measures and curtains.