At the time of user creation, you have to assign a profile to each user.
Profiles define how users access data and objects , and for what they are permitted within the application.
Your organization includes several standard profiles, in which you can edit a limited number of settings.
In Enterprise, Performance, Unlimited, and Developer Edition organizations, you can use standard profiles or create custom profiles.
In custom profiles, you can edit all permissions and settings except the user license.
In Contact Manager, Group, and Professional Edition organizations, you can assign standard profiles to your users, but you can't view or edit the standard profiles and you can’t create custom profiles. Every profile belongs to exactly one user license type.
Salesforce has two profile interfaces. Depending on which profile user interface is enabled in your organization, you can:
Enhanced profile user interface profile overview page provides an entry point for all of the settings and permissions for a single profile.
To open the profile overview page, from Setup, click Manage Users -> Profiles and click the profile you want to view.
From the profile overview page, you can:
--> Search for an object, permission, or setting.
--> Clone the profile.
--> If it's a custom profile, delete the profile by clicking Delete.
--> Change the profile name or description by clicking Edit Properties.
--> View a list of users who are assigned to the profile.
--> Under Apps and System, click any of the links to view or edit permissions and settings.
To view a profile, from Setup, click Manage Users -> Profiles, then select the profile you want.
On the profile detail page, you can:
--> Edit the profile.
--> Create a profile based on this profile.
-->For custom profiles only, click Delete to delete the profile.
--> View the users who are assigned to this profile.