A banner is the result of Shodan crawling a service/ port on an IP. For example, a HTTP banner would be the HTTP Header that gets returned from a website ala:

A banner is the result of Shodan crawling a service/ port on an IP. For example, a HTTP banner would be the HTTP Header that gets returned from a website ala: HTTP/1.1 200 OK Server: Apache ... The banner includes metadata about the service/ software that is running on the device.