Strength and conditioning is essentially exercise used as physical preparation for specific tasks and activities. The goal is to improve physical capacity and performance in relevant ways to carry over into those activities.
This can be applied to a broad range of people and activities. For example an elite level rugby player may use S&C in the form of gym exercise to improve their performance on the pitch, but it could also be applied to more everyday tasks like someone who wants make it easier to carry their young kids around, or be able to do some hiking on the weekends.
The exercises used in S&C are varied and dependent on the individuals goals, but may be focused around improving strength, endurance, mobility, flexibility, speed, power and agility.