This help article details how to create a new platform user in salesforce, from start to finish, using simple steps.
What is a Platform user ? :
Users with a Salesforce Platform user license can access all the custom apps in your organization. Although normally the platform user starts with limited access and access is granted to by the administrator(s). A user’s level of access is slightly less than an administrator and salesforce assign a smaller number of administrators and a larger number of platform users.
How to create: