Maximum strength is defined as the ability to produce maximum force in a single effort. Muscular endurance is defined as the ability to produce force repeatedly over an extended period of time.
The concept of muscular strength is best understood as the maximum amount of weight that a given muscle or group of muscles can withstand. Exercises that target strength focus on increases in the amount that a group of muscles can lift for a single repetition.
Related to strength, stamina is best understood as the amount of time that a given muscle or group of muscles can perform at maximum capacity. If you can perform a single bicep curl of 25 kg kgs, you may have stronger bicep muscles than someone whose maximal bicep curl is 20 kgs, but the other person can be said to have greater bicep stamina if he can perform more repetitions at this maximum weight.
It is important to train both in some amounts - it is not only about maximums, but feeling good and having a good life in body you enjoy.