Pruning plants involves strategically removing parts like branches, buds, and roots to enhance aesthetics, promote health, and restrict unwanted growth. It should be done according to safety procedures and using the proper tools for each task, such as secateurs for small twigs, long-handled pruners for branches up to 40mm, aerial pruners for high branches, handsaws for branches over 50mm, hedge shears for shaping plants under 1cm, and pruning knives for beveling cuts. Reasons for pruning include training plants, maintaining health, improving quality, and restricting growth.