Haha, you only want to know everything…
Well here is a Basic rundown
- HF (13.56MHz)
- ISO14443A
- NFC Type 2 compliant
- NTAG I2C
- 7 byte UID
- 2kB (1912 bytes)
- Blinky
All of those are clues as to what you can do with it
ie. What you can use to interact with it
Like what @Eriequiet and @Locutus said above
A good example is the NFC, which your phone will likely have, this is what NDEF ( NFC Data Exchange Format )
So you can do things like this
using something like TagWriter
The 2kB of memory split is usable, however only 1kB can be used for NDEF, are you familiar with NTAG I2C.?
As you have already bought the xSIID you will still get the full 2kB to play with, I believe in the future the new ones will only be 1kB, let me find the link from Amal…
Generally, if you go to the product page, all the information should be there, or at the least the clues.
https://dangerousthings.com/product/xSIID/
The best idea would be to search through the forum 
and read what others have posted.
and follow their links
like this