To understand the division, you need to first think back to the history of development in this area. Before non-native development the mobile market was split between responsive mobile websites and native applications. Responsive sites hit the broadest audience and have comparatively easy deployment; just update in one location and all users immediately have the latest version. This can have varying levels of success but despite that, has been the go-to option for most small or medium enterprises.
Native applications have to be downloaded and, although promoted through the various review platforms and the stores they rest in, not every customer is able to find or use your app - so there’s an immediate loss to your market. Despite this, those who do find the app will have a much better user experience with the additional features and tailored approach, which is a primary driver to greater success and retention of customers. All of this comes with a time commitment as every update on the web UI will have to be coded separately into the mobile solution and deployed.
So, back then, most companies built increasingly responsive websites to provide universal access whilst some went to the next level: responsive applications and building a native application to provide a better user experience and gain exposure through the app stores. They could then use their website to assist customers in finding the application (through links to the app store, or even a hyperlink to the mobile version) and create a greater, overall experience and customer journey - something you’ll no doubt have seen at some point.