401(k) plan:

A qualified plan established by employers to which eligible employees may make salary-deferral (salary-reduction) contributions on a post- and/or pre-tax basis. Employers may make matching or non-elective contributions to the plan on behalf of eligible employees and may also add a profit-sharing feature to the plan. Earnings accrue on a tax-deferred basis.

403(b) plan:

A 403(b) plan, also known as a tax-sheltered annuity (TSA) plan, is a retirement plan for certain employees of public schools, employees of certain tax-exempt organizations and certain ministers. Individual accounts in a 403(b) plan can be any of the following types:

An annuity contract, which is provided through an insurance company,

A custodial account, which is invested in mutual funds or

A retirement income account set up for church employees.

Generally, retirement income accounts can invest in either annuities or mutual funds.