The present invention relates to a method, an apparatus, a system, and a computer program in which a server offers product information corresponding to an image displayed on a client and the client displays the product information. A method for offering product information by a server to a client includes: generating a database on a plurality of products and extracting feature information on an image included in the database; receiving an image displayed on the client as a query image from the client; determining a matching product matched to feature information on the query image by retrieving feature information on the image in the database; and offering information on the matching product to the client. According to the present invention, the server may retrieve a database of product information only with an image displayed on the client and may offer product information to the client.