This are the main ones I know used by hostels
I believe Hostelsystem, siteminder, hosteloffice and charts all have their own channel managers integrated with them.
I know loventis and bananadesk connect to myallocator.
So firstly the main thing to have is a channel manager. This is what saves you have to change availability once you get a booking.
So for instance a customer books through hostelworld then the channel manager will remove that available bed or room from the other channels such as booking.com or your own website.
The channel manager will usually have its own booking widget which will let people book directly through your own website.
Now for the PMS system. The channel manager does not easily show you booking information in a calendar form such as peoples names and how long they are staying.
You can easily see this information on your PMS system including how they booked and how much they owed. Also you can easily input new arrivals via walk in or on the phone and once that data is put in through your PMS it feeds it into the channel manager which then removes availability from the different channels. You can also run repots and see how much money you have taken in or what revenue you are getting per bed. Some PMS systems are able to send auto emails to guests when they book or after check in requesting reviews. There are extra features in the bigger ones but I guess it is down to the money you want to spend.
What some people will do is manually enter the data in to an excel sheet in stead of using a PMS system.
Here is a video from Hostelmanagement that was done a while back in regards channel managers