Well, before explaining what profiles are, let me tell you one sentence which gives you lot of confidence and never forget again.
Roles in Salesforce define what a Salesforce user can view with in Salesforce application & Profiles in Salesforce define what a Salesforce user can do with in Salesforce application.
Is it clear from the above statement? Roles is about what an user can see? and profile is about what an user can do with what he is seeing..
Now let’s see what Profiles in detail. Profiles are a set of settings and permissions that will help a user in salesforce can do to an object, or records, tabs, passwords, page access etc..
With profiles we can configure tabs, apps, objects, record settings, page layouts, field permissions, manage cases, leads, password policies etc..
So, how many types of profiles in Salesforce?
There are two types of profiles in Salesforce, 1. Standard profiles, 2. Custom profiles. We can clone standard profiles to make a custom profiles.
Why we need custom profiles? Custom profiles are useful to give permission to custom apps, custom settings, etc..