The kit comes with the board with the LoRa module (pre-installed with Meshtastic) plus two small antennas, one for Bluetooth and the other for LoRa.

In addition to the items I mentioned in that note, this is the antennna that RAK sells - pick the correct frequency for your region:
https://store.rakwireless.com/products/blade-antenna
(I only bought the antenna elsewhere because I forgot to add it to my order).

You can also add the GPS module if you want to transmit location and some of the sensor modules that RAK sells are also supposed to work with Meshtastic although I haven’t tried this yet.

A couple of other things to mention are that a small amounting of soldering is needed with the RAK system to attach the OLED display and also they don’t include WiFi.

If you want something that is ready to go and also includes WiFi then the LILYGO TTGO T-Beam is another option:
https://www.aliexpress.com/item/4001178678568.html