What is the difference between baking and roasting?

Both use dry heat in an oven, and the distinction is largely convention with a real technical core. Roasting typically means higher temperatures, usually above 400 degrees, applied to foods that already have a solid structure, meat, whole vegetables, poultry, with the goal of browning the exterior through the Maillard reaction and caramelization while cooking the interior. Baking generally means moderate temperatures applied to foods that begin as liquid or soft batters and doughs and develop their structure during cooking as proteins set and starches gelatinize.

The overlap is where the argument lives, since baked chicken and roasted chicken are the same operation and nobody says roasted bread. A more useful practical distinction for cooking well: high heat and space around the food produce browning, while moderate heat and crowding produce steaming. That is why roasted vegetables come out limp and pale when the pan is overloaded, since the moisture they release cannot evaporate and they cook in their own steam. Convection, which circulates air with a fan, effectively raises the browning power at the same temperature, which is why convection recipes usually call for reducing the temperature by around 25 degrees. Broiling is a third mode entirely, using intense radiant heat from above, and it browns surfaces quickly without cooking anything through.