It describes the quality of something being more powerful or intense than something else.
Here's how you might use it in a sentence:
* The lion is stronger than the tiger. (Here, "stronger" compares the strength of two animals)
* This rope is stronger than the other one. (Here, "stronger" compares the durability of two ropes)
* I feel stronger after a good night's sleep. (Here, "stronger" describes a feeling)