First is understanding that RFID is very generic term. NFC is subset of RFID technology. NFC is used for prox card, credit cards, tap and go payment system. Your phones can read and emulate NFC (Apple pay, Google pay, etc.), if they support NFC. NFC is very short distance and low power - which is why you see tap and go type usage.
The more common RFID are the tags you see here and there. They come in a wide ranges of styles, uses and frequency.
HF - high frequency tags are what they use for "chipping" animals - cattle, dogs, cats. Read range is about 12 inches and requires an external antenna that is powered the bigger the antenna the more power it needs and the further it can read.
UFH tags look similar to HF tags but have a read range of several feet.
Also HF tags come single read and multi read. UFH is exclusviely multi read.
Mutiread means when a reader is active, you can litterally read about 1700 tags in under 10 seconds.
But this is a function of the size of the antenna and how much power you can push through the reader.
As to the direct question about Android and RFID - the best way to go is to get an external handheld reader that connects to your mobile device via Bluetooth. Bluetooth libraries exist for all mobile devices - Android, Apple, Windows. From there its just a matter of the manufacturer documentation about how to open a socket to the reader and how to decode the serial information.
The TSL line of readers is very popular because you don't have to deal with reading bytes and all that low level serial jazz that other manufactures do. They have a nice set of commands that are easy to use to control the reader.
Other manufactures are basic in that you open a serial socket and then read the output like you would see in terminal app like PuTTY.