As per the official docs,
In App Service, an app runs in an App Service plan. An App Service
plan defines a set of compute resources for a web app to run. These
compute resources are analogous to the server farm in conventional web
hosting.
When you create an App Service plan in a certain region (for example,
West Europe), a set of compute resources is created for that plan in
that region. Whatever apps you put into this App Service plan run on
these compute resources as defined by your App Service plan
For answering your question which is mostly depends on the pricing tier which you have chosen
- Shared compute: Free and Shared, the two base tiers, runs an app on
the same Azure VM as other App Service apps, including apps of other
customers. These tiers allocate CPU quotas to each app that runs on
the shared resources, and the resources cannot scale out.
- Dedicated compute: The Basic, Standard, Premium, and PremiumV2 tiers
run apps on dedicated Azure VMs. Only apps in the same App Service
plan share the same compute resources. The higher the tier, the more
VM instances are available to you for scale-out.
- Isolated: This tier runs dedicated Azure VMs on dedicated Azure
Virtual Networks, which provides network isolation on top of compute
isolation to your apps. It provides the maximum scale-out
capabilities.
- Consumption: This tier is only available to function apps. It scales
the functions dynamically depending on workload. For more
information, see Azure Functions hosting plans comparison.
For the slot settings as well, it will share all the resources from the App Service Plan