Generally, "International" refers to a GSM-capable device that is unlocked for use on any carrier. The International GSM+LTE edition of the Galaxy Tab S2 is model number SM-T815 and, of course, comes with an LTE modem and SIM card slot onboard.
There are variants for each carrier. Generally, AT&T takes the model number and adds an A to the end, T-Mobile adds a T, etc.
The Wi-Fi only model is the SM-T810
The unlocked international LTE model is the SM-T815
The AT&T cellular model is the SM-T817A
The T-Mobile cellular model is the SM-T817T
The Verizon cellular model is the SM-T817V
The Sprint cellular model is the SM-T817P