A plural refers to more than one person or thing; feminine concerns the feminine gender; and sound indicates that the singular word’s basic form is largely preserved.
مُسْلِمَةٌ ← مُسْلِمَاتٌ — one Muslim woman → Muslim women.
طَالِبَةٌ ← طَالِبَاتٌ — one female student → female students.
مُعَلِّمَةٌ ← مُعَلِّمَاتٌ — one female teacher → female teachers.
These are common formations. Not every word ending in «ات» is automatically a sound feminine plural; check its singular and pattern.