You might be aware of the fact that in SharePoint 2013, Microsoft introduced the APP Part to develop the APPS. The major differences between the App Part and the Web part are the following.
- An App webpart can run outside the SharePoint environment, but the Web Part has to run under the SharePoint premises.
- An App webpart can be deployed to the Cloud premises, but a web part has to be deployed in the OnPremises server.
- If an App web part crashes, it won't significantly impact the SharePoint farm, whereas, in case of the webpart, it does affect the farm.
- Apps can be deployed to the Microsoft Office Store.