In general, the term OTA implies the use of wireless mechanisms to send provisioning data or update packages for firmware or software updates to a mobile device — this is so that the user does not have to go to a store or a service center to have applications provisioned, parameters changed or firmware or software
Just so, can we get official updates after rooting?
The answer is simple you can't update a rooted phone using the standard method. Instead, you have to use either the Samsung Kies or Mobile Odin Pro to flash the new Android version, but you lose root access. Once that's done, you'll have to reroot your device.
What is Flashfire?
FlashFire is the most advanced on-device firmware flasher available for rooted Android devices. It can flash full firmware packages from various manufacturers, as well as apply over-the-air (OTA) and ZIP updates - all while maintaining root, and without using a custom recovery.