A mala uses various counter and spacer beads to bring the mind back to the practice of chanting mantras during meditation. When we are meditating the mind can stray off as your focus goes very deep internally. The counter beads bring our awareness back to our Sanskrit mantra and to our practice.
Check out https://japamalabeads.com/how-to-use-a-mala/ this gorgeous infographic on how to meditate using mala beads.