Strength is not Power.
Power is not Stamina.
Stamina is not Strength.
But they are connected in someways
Strength refers to the force generated to overcome a given level of resistance. When a given load is moved, it so happens with the force generated from the muscles. The force generated is equal to the load being moved.
This force is generated within the muscles which is referred to as strength of a muscle. The higher the level of resistance, heavier the load, more force required to move the object, more force generated within the muscle and hence, stronger the muscle.
Based on load and body position in space, strength can be categorized as either absolute or relative.
Absolute Strength refers to the strength of a muscle when an external object is being moved while the body is not in motion. Example Bench Press, Lat Pull Down, Deadlifts, Leg Press
Relative Strength refers to the strength of a muscle when the body moves through space along with the external object/load (if any). Example Pushups, Pullups, Squats, Lunges, etc.
In simple terms, Strength refers to the Amount of Load being moved.
Power refers to how fast the load being moved. In other words, Power is the Force Production divided by Speed of Execution. It is measured by in terms of How heavy a load is being moved and how fast? The two components of Power being Speed and Load. Think of Olympic lifters moving super-heavy loads with a lot of explosive strength.
Stamina refers to how long is the load being moved. In other words, Stamina is the result of Strength multiplied with the duration of application of strength. Stamina or Endurance can be measured by multiplying Strength with the number of times Strength was applied.
As it can be seen, foundational strength is the base for all the other attributes to build upon. Hence, Strength is not the same thing as Power or Stamina.
Resistance Training vs Cardio
This is an area where people have a brief idea of what these mean and how they differ from each other but have no clue about how similar and interlinked they are, despite being different in their utilization of energy systems of the body.
Resistance Training simply means any sort of physical training where the resistance is used to build the body in any of the aforementioned attributes. Here the key aspect is that a given resistance or load is being overcome with the application of strength generated by the muscles. This explains why Resistance Training is also called Strength Training, very often. Example: Weight Training, Calisthenics, Gymnastics, etc.
Cardiovascular Training or Cardio means any sort of physical activity/training where the cardiovascular system is primarily targeted. Cardio training utilizes the aerobic energy system of the body, hence challenging the cardiovascular system. For example: Running, Stair Climbing, Walking, Jogging, Jump Roping etc.
Everybody understands this in a nutshell but the way these two overlap is something not many understand.
Resistance Training also taxes your heart via aerobic system if it is carried out for too long in which case the load has to be low enough to not use the anaerobic system in the first place. In other words, A Squat can also act like a Cardio exercise if the weight is not too heavy and too challenging.
Cardiovascular Training is simply a low load version of Resistance Training carried out for too long to be able to tap into the Aerobic System instead of Anaerobic System.
Similarly, Cardio Training like Running can be turned into Resistance training by adding external load to it. Think Farmer Walk. You know that is one hell of an exercise to start panting with, yet still be able to go heavy with. A heavy farmer walk can neither be done for too long nor can it be done with too heavy a load. When a sweet spot is achieved, Farmers Walk works the best, it taps into both the energy system sequentially. In such a case, the line between Resistance vs Cardio Training is blurred.
It is safe to say that when Load is high and Duration of exercise execution is low (<60 seconds), it can be termed as Resistance Training, while when the load is low and the duration of exercise execution is longer than (>3 minutes), it can be termed as Cardiovascular Training.