Hai @Tray10. Farisya here. 
 
PMS is a system for hotel to manage front office tasks for example create reservations, handle guests' check-in and check-out, assign room, housekeeping, reporting and many more. 
To sync the calendar and price across multiple channels like OTAs, you will need to have a Channel Manager. Hence, you should look for a PMS that can be integrated to the Channel Manager. 
I recently write an article about PMS and its important features. I believe this will be useful for you while reviewing which PMS that you want to choose. Have a good day!