Modern day tandoors for home use or restaurant use are operated on electricity or gas. Only a few of us these days, however, are lucky enough to have our own charcoal tandoor. Barbecues can be pretty good, especially where cooking can be done over a grill that lets food juices run onto the burners or coals. The effect is not quite that of the tandoor, but the resulting flavour is acceptable.
You could choose a conventional oven to cook tandoori dishes. The similarity here is that both the oven and the tandoor have an enclosed space where heat is trapped, but the former does not produce the trademark smoky flavouring of real tandoori food. This method is the best alternative for cooking tandoori breads (naan, roti, kulcha etc), when a tandoor is not available because the bread is surrounded by heat.
A grill can be used when cooking food like lamb chops or chicken tikka even though the concept of grill cooking is really the reverse of tandoori cooking. A grill does not have an enclosed space and food is heated by elements from above. Nevertheless, we can cook some tasty food on the grill. The grill is good for quick cooking especially when the barbecue is not an option.