A more thorough explanation:

Definition: A Treasury Bill, also known as a T-Bill, is a type of security issued by the U.S. federal government. It is a short-term investment that can be bought for as little as four weeks or up to a couple of months. Treasury bills are considered one of the safest investments in the world because they are backed by the U.S. government.

When you buy a Treasury Bill, you are essentially lending money to the government. In return, you receive interest payments and the face value of the bill when it matures. The interest rates on Treasury Bills are typically low, ranging from 0.03% to 0.075% in 2021, depending on the length of the maturity.

You can buy Treasury Bills in a few different ways. You can bid for them at a government auction, purchase them through a third-party like a bank, or buy already issued bills on the resale market.

Treasury Bills are one of three main securities issued by the U.S. federal government, with the other two being Treasury Notes and Treasury Bonds. However, Treasury Bills have the shortest maturity period and the lowest interest rates.

Let's say you have $1,000 that you want to invest in a safe and low-risk option. You decide to buy a Treasury Bill with a maturity period of four weeks. The interest rate on this bill is 0.03%, which means you will earn $0.30 in interest over the four weeks. When the bill matures, you will receive the face value of $1,000 back.

This example illustrates how Treasury Bills work as a short-term investment option with low interest rates but high safety and reliability.