What are Login Hours and Login IP Ranges in Salesforce?

You can restrict the hours during which users can log in and the range of IP addresses from which they can log in and access Salesforce. If IP address restrictions are defined for a user’s profile and a login originates from an unknown IP address, Salesforce does not allow the user to log in. These restrictions help protect your data from unauthorized access and phishing attacks.
Login Hours
For each profile, you can set the hours when users can log in. See:
View and Edit Login Hours in the Enhanced Profile User Interface
View and Edit Login Hours in the Original Profile User Interface
Login IP Address Ranges
For Enterprise, Performance, Unlimited, Developer, and Database.com editions, you can set the Login IP Range addresses from which users can log in on an individual profile. Users outside the login IP range can’t access your Salesforce org.
For Contact Manager, Group, and Professional Editions, set the Login IP Range. To set the range, from Setup, enter Session Settings in the Quick Find box, then select Session Settings.