The main difference between combustible and non-combustible tobacco is that combustible tobacco products require fire to burn the product to then be consumed whereas a non-combustible tobacco product requires no burning at all.
Non-combustible tobacco products are products that do not require burning of the product, such as a tobacco heat stick that goes into a heat-not-burn device.
A combustible tobacco product is effectively what traditional smoking products are. These products require them to be burnt to be consumed, such as cigarettes, cigars and cigarillos.