To reduce the size of the Apps in your iPhone, start by deleting the apps you never use. There is also the option to offload redundant apps- this erases the app but retains your data. If possible, clear the cache and remove data (videos, documents, etc.) in the app. This relieves storage. If you’re asking what does Applications mean on iPhone storage, it simply includes all your installed apps and their data. They can be cleaned up to make your iPhone run faster.