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standard features are defined by PWR Apps and hence available throughout the org.
Custom feature
custom features are those defined by you while creating an application, as they are custom feature names of the feature will be prefixed with instance prefix.
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The number type of feature indicates the number of APIs can a user use using that feature. for example, user to which this feature's license is assigned can consume n APIs per day, after that he will get an error that his allocated amount is exhausted.
API:
API type of feature indicates a number of APIs users can have access to. for example, all users together in the instance can consume max n API per year, after that, they will get an error that allocated calls are exhausted.
Storage:
Reset Period
Never:
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There will be some features that will get reset daily i.e after every 24 hr. for example API usage have to be reset on the basis of the day (24 hr).
Annual:
There will be some features that will get reset annually, for example, there are some APIs whose usage has to be reset annually.
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