The Thrift Savings Plan (TSP) is a retirement savings plan sponsored by the United States Federal Government. It is designed to provide retirement income to employees of the federal government, uniformed services and their families. It is similar to a 401(k) plan offered in the private sector but with some key differences.

One of the main benefits of investing in a TSP is an immediate tax break on your savings. This gives participants the opportunity to save money tax-free and/or defer taxes until they start withdrawing their savings during retirement. Participants can also opt to invest in a Roth contribution, which will offer them tax-free withdrawals after retirement.

In terms of investing options, participants can put their money into any of six different funds offered by the TSP. These include the G Fund, which is a stable security option; the F Fund, which is an equity index investment; the C Fund, which is a common stock index; the S Fund, which is a small capitalization index; the I Fund, which is an international stock index; and the L Fund, which is a life-cycle fund with varied asset allocations that depend on when participants are planning to access their money in retirement.

Participants in the TSP also have the option to move their money between funds or even to a different 401(k) or IRA if they leave working in the public sector for the private one. If a participant leaves a public service job, they can move their money to but not from a 401(k) or IRA.

Overall, the Thrift Savings Plan is an excellent choice for federal employees and military members who want to save for retirement. It offers tax-deferred savings, the opportunity to invest in different funds, and lets participants roll over their money if they leave the public sector. It's important to note, however, that any decision regarding retirement savings should be made in consultation with a financial advisor.