How an internship offer differs from a job offer
An internship is a fixed-term learning role, so the letter has an end date and no probation. Interns are paid a stipend rather than a salary, so there's no CTC, no salary annexure and no PF deduction.
Many interns need the letter for their college as well, to show the internship is approved and has a fixed duration, so make the dates and the name of the organisation clear.