In general, there are six ways to classify skills: environments, muscles, skill targets, movements, simplicity and pacing. Each is a dimension, not a categorical dichotomy. It is not either-or but how much of this factor is involved.
Environments can be open or closed. Closed environments are predictable. Movements can be planned in advance. Examples include chess, gymnastics, and figure skating. A pianist playing classical music is a closed environment.
In contrast, a pianist playing jazz is an open environment. Open environments require dynamic adjustments to changing conditions. They are unpredictable. Examples include debating, boxing and horse trading.
Obviously, many tasks combine both open and closed environmental factors. Standup comics plan their joke sequence ahead of time but have to handle current events, theater conditions and hecklers. Creating a well-planned set is a closed skill but improvisations is an open skill.
Muscles. Skills can also be classified on basis of which muscles are employed. Gross motor skills use large muscles. These are the muscles you use to sit, kick a ball or maintain balance. In contrast, fine motor skills are required for writing with a pencil or picking lint off the carpet.
Gross motor skills are the first to develop in children, with fine motor skills coming somewhat later. Boys tend to develop fine motor skills later than girls but the sexes are equal by about age 5 or 6.
Targets. Skills can be classified by targets. Target skills are the actual tasks needed to accomplish a goal, such as keeping a tennis ball in play. Target behaviors are the component actions needed to perform target skills, such as watching the ball, and keeping the wrist firm. Target contexts are the environments in which you perform a skill. A friendly game of golf is quite different from a competitive tournament.
Movements. Skills can also be classified by type of movement: continuous, discrete, serial or mixed. Continuous movements are cyclical. There is no clear beginning or end. They include swimming, cycling and steering a car. Discrete skills have well-defined actions. There is a clear beginning and a clear ending. Discrete movements are independent actions, such as typing, hitting baseballs and pounding nails.
Serial skills are sequences of discrete movements. Serving in tennis requires tossing the ball up, swinging the racket and follow-through. It is not a continuous swing like a figure-8 would be. Although practiced together, the sequence has discrete component parts.
Mixed skills are a combination of discrete and continuous movements. It is clicking the shutter while taking a photo of a moving object you have to track. Shooting space aliens in a video game requires both flying the ship (continuous) and triggering the blasters (discrete). CPR requires giving chest compressions (discrete) and mouth to mouth artificial ventilation (continuous).
Simplicity. Simple skills can be discrete or continuous. They are tasks which require little thought or physical energy. Examples include flipping a light switch, a flick serve in badminton, and pushing the doorbell button. In contrast, complex skills require timing. Changing gears in a stick-shift care involves pushing in the clutch (discrete) and shifting gears (discrete) but the timing is critical. A lay-up in basketball is more complex than a free-throw. Twirling a Hula-Hoop on each arm is a complex skill composed of two simple continuous movements.
Pacing. Skills can be either self-paced or externally-paced. Self-pacing skills are performed when you want. You can let the chess clock wind all of the way down before you move or make the move quickly. You decide when you are ready to start your speech. You can do all of your planning ahead of time and then initiate your long jump or ring routine. In contrast, when environmental factors trigger a response, you are engaged in an externally-paced activity. Examples include driving when the light turns green, countering an attack or being forced to pass the ball before a linebacker sacks you. Externally-paced skills are time sensitive. They require immediate attention.
All six dimensions help us to understand the characteristics of a given skill. Most skills are a mixture of factors. And that mixture changes. Tasks which are complex and externally-paced might be less so the next day. You might have an easy comeback to an insult one day and find it terribly difficult to respond the next day. Thinking about the nature of the skills we use can help us focus our practice and improve our game.