The profile in Salesforce is defined as a collection of settings and permissions that define what a user can do in Salesforce. So it gives you the authority to access certain records in Salesforce. There are multiple profiles available in Salesforce. For example, a sales profile can have access to leads, contacts, campaigns, opportunities, etc.
The people who work under one department may be assigned the same profiles. Consider the case of sales profile, many people work under it and each person who works under this is assigned with the same profile. Hence we can say that any number of people can have the same profile.