BLE Property explanation

I was working on ESP32-Wroom series arduino board. I checked the default BLEServer example and then there was a property defined as PROPERTY_NOTIFY. I was checking the example on my Android phone but I wasn't sure what does it mean. When I changed this property to PROPERTY_READ then I was able to read the characteristics on the phone but it wasn't getting updated itself, I have to read this property manually. Can somebody put some light on these properties, what could be the best use of these properties?