Letter of Resignation is an official document provided by the employee to the employer when he wants to terminate his employment with the company. Letter is basically an advance notice to the company about the resignation so that the organization gets prepared and should not have any loss in the productivity. Although there can be an oral notice about the resignation but giving letter is a better option for the employee to be very clear with all the information like last working day and is also good for the organization as it helps in keeping track of records.
The employee may have verbally informed his employer about the reason for resignation but employer can never ask an employee to document the reason on paper. After the discussion about reason for resignation the employer may agree to the terms and condition of employee and employee may take back his resignation. Resignation letter can be used as reference in the coming future so it has to be written in such a way that it is always taken positively and should never be misunderstood.
If the organization is having the clause of notice period then the employee have to serve that notice period to the company after handing over the resignation letter like if the notice period is 15 days then he can leave only after serving 15 days from the day he handed over the Letter of Resignation. Employees are very smart these days so they keep their resignation letter very simple and straight forward without mentioning any extra information that nothing can go against them during background check from other companies.