Meaning: She moved through the water using her arms and legs in a pool to stay fit.
Choice of Words: Swam is a past tense verb that means to move through water using your arms and legs. Laps are lengths of a swimming pool. Exercise is a noun that refers to physical activity done to stay fit.
Alternative Expressions
The girl did laps in the pool as a workout.
Meaning: This sentence means the same thing as the first sentence, but it uses different words to describe the person and her activity.
Choice of Words: **Girl** is a noun that refers to a young female person. **Did laps** means that she swam back and forth across the pool several times. **Workout** is another word for exercise, which means any activity that makes your body move and work harder.
She exercised by swimming laps in the pool.
Meaning: This sentence also means the same thing as the first sentence, but it uses different words to describe the person, her activity, and where she was doing it.
Choice of Words: **Exercised** is a verb that means to do something that makes your body move and work harder, like swimming. **By swimming laps** means that she swam back and forth across the pool several times. **In the pool** tells us where she was swimming.