Sally,
Cletus has made a good point, any NAS requires technical knowledge or, at least, a degree of technical curiosity. If you are not technically minded, maybe a NAS is not for you unless you know somebody who can help. Having said this once installed and configured they are very simple to use; mine even has the option of telling it when to switch off or on each day of the week. Of course if something goes wrong with the NAS, you might need help.
My only concern with the Time Capsule is that it is not redundant storage, it does not support RAID. Conceptually RAID is not very complicated, take RAID 1 as an example, if you have a Synology NAS with 2 disks, just to keep it simple, of 2TB each, you have 4TB of raw storage. Now, if you configure the NAS storage for RAID-1, the NAS would write each backup twice, once per disk. The logic behind it is that it is less probable to have 2 disks fail simultaneously than 1. In the event of a single disk failing, the Synology NAS would still be able to recover a backup from the 2nd healthy disk.
Something I would recommend researching are warranties. I opted for La Cie, instead of Synology because of the warranty, but Synology is good.