The 403(b) plan is a tax-deferred retirement savings account that's offered through nonprofit employers, such as public schools, hospitals and religious institutions. The plan was created in 1958 and allows employees to save for retirement on a tax-deferred basis. Employees who participate in the plan may be able to keep their contributions from being taxed until they take withdrawals during retirement. The money in this type of account can also be invested in mutual funds or other types of investments.