This is the 7689th most frequent Russian word.
заниматься
To engage in, to occupy oneself with, to study, or to practice.
In this sentence, 'заниматься' means 'to engage in' or 'to practice', used with sport activities.
Я люблю заниматься спортом.
I love to engage in sports.
Here, 'заниматься' signifies dedication to practicing music or learning about it.
Она хочет заниматься музыкой.
She wants to engage in music.
In this example, 'заниматься' indicates a commitment to the activity of studying.