Can two users have the same profile and two profiles be assigned to the same user in Salesforce?

Profiles determine the level of access a user can have in a Salesforce org.

As far as the first part of the question is concerned, Yes. One profile can be assigned to any number of users. Take the example of a Sales or Service team in a company. The entire team will be assigned the same profile. The admin can create one profile: Sales Profile, which will have access to the Leads, Opportunities, Campaigns, Contacts and other objects deemed necessary by the company.

In this way, many users can be assigned the same profile. In case the team lead or manager need access to additional records/ objects then it can be done by assigning permission sets only for those users.

Answering the second part of the question, each user can only be assigned 1 profile.