Foam-backed carpet, generally, has a bad name on the domestic front!
On the contrary, there are many foam-backed carpets manufactured to very high standards.
As with tufted (or secondary) backed carpets, there are cheaper-end as also, more expensive foam-backed carpets.
At the better end of the range, there are quality carpets costing more than a lot of tufted's.

The big difference between foam-backed and tufted, is that the tufted has another more stable backing
adhered at manufacture to add strength and stability, whereas the foam-backed has a layer of foam or rubber adhered instead, which acts as the underlay..
The obvious advantages of choosing foam-backed carpet is the initial low-cost and savings on underlay.
Depending on the circumstances, i.e. wear due to heavy traffic, the cost-savings can easily be outweighed, due to excessive use, so you must bear this in mind!

Carpet's