There are slight differences between the two, but usually that can be used interchangeably. Bongs are usually used with dry herb while dab rigs are used with wax/oils. For bongs and dry herbs you use a bowl and for dab rigs you will usually use a banger nail with the wax. The biggest difference of the two is that dab rigs are usually shorter and bongs are taller. This is because the herb can last longer without losing potency while for dab rigs the oils/waxes need shorter distances to stay potent.