Interstitial lung disease” is not a separate disease, but a general term for a large group of diseases. Interstitial pneumonia is medically classified as a diffuse interstitial lung disease (interstitial lung disease), and in recent years has also been referred to as a diffuse substantive lung disease. There are many causes of interstitial pneumonia, including environmental, occupational, physical, and chemical factors, such as frequent exposure to asbestos and mineral dust at work, chemotherapy drugs, and inhalation of harmful gases. Exogenous allergic alveolitis caused by exposure to pigeon droppings, animal fur, moldy wilts, etc., can lead to interstitial pneumonia. Some rheumatic immune diseases (e.g., systemic lupus erythematosus, rheumatoid arthritis, dry syndrome, dermatomyositis, scleroderma, etc.) can be accompanied by interstitial pneumonia. Those manifestations of interstitial pneumonia of unknown origin are called idiopathic interstitial pneumonia, including idiopathic interstitial pneumonia as well as the relatively rare nonspecific interstitial pneumonia and cryptogenic mechanized pneumonia. The initial clinical diagnosis of interstitial pneumonia is made by chest radiograph and lung CT, but imaging findings alone do not provide a complete picture of the disease. In outpatient clinics, we see patients with chest films and CT films who say they have interstitial pneumonia. In fact, interstitial lung changes on chest films or CT films do not necessarily mean interstitial fibrosis or interstitial lung disease, as many lung diseases can cause interstitial lung changes, such as tuberculosis or pneumonia, which can leave interstitial lung changes after recovery. In addition, chronic obstructive pulmonary disease, bronchiectasis, pulmonary small vessel vasculitis, and even chronic cardiac insufficiency can cause similar interstitial lung changes, which are sometimes misdiagnosed as interstitial pneumonia. Ancillary tests to diagnose interstitial pneumonia or interstitial lung disease include pulmonary function tests, various blood tests, bronchoscopy-related tests, and lung biopsy. It is often said that “there is no cure for interstitial pneumonia” or even “you can only live for three to five years at most”, which is incomplete and unscientific. Idiopathic interstitial pneumonia is one of the many types of interstitial pneumonia with an unknown cause and typical clinical manifestations and CT features. Targeted treatment for this disease currently includes pirfenidone, the efficacy of which remains to be seen, but the rate of disease progression does not vary from patient to patient. Clinical observations abroad have found that the median survival of patients is about 5 years, which is only a statistical figure, but in fact many patients survive for much longer than 5 years. Non-specific interstitial pneumonia and cryptogenic mechanized pneumonia, which are in the same category as idiopathic interstitial pneumonia, are often effectively treated with medications, especially cryptogenic mechanized pneumonia, which has a good prognosis. In addition, many of the cases of interstitial pneumonia often seen in clinical practice are secondary. If it is clear that interstitial pneumonia is caused by a rheumatic immune disease, the focus of treatment should be on the primary disease, which is reduced, and interstitial pneumonia may subsequently improve. Some interstitial pneumonia caused by environmental factors can remain relatively stable for a longer period of time after removal from the corresponding environment. There are also some types of interstitial lung disease (such as nodular disease) that can be significantly improved or even cured by glucocorticoid and immunosuppressive therapy. This shows that for interstitial pneumonia and interstitial lung disease, it is crucial to clarify the cause of the disease in order to achieve better results.