What's the difference between chest X-ray and chest CT?

Chest radiograph belongs to ordinary X-ray photography, and CT is a tomographic scan of the chest. Both of them need radiotherapy. The latter has more radiation, clearer observation of lesions and stronger discovery of tiny lesions than the former. The advantage of chest X-ray is that it is relatively cheap, and it can be used as a routine examination for admission or outpatient service, and further CT examination can be done if necessary.