You can buy and sell them just like stocks.

But each one has a maturity date. If you still own it on that date, it goes away and you get your $1000 deposited into your account, which you can use to buy a new one. Or not.

If all you own are the bills, that means that none of them will last a long time before they turn into cash - they aren’t as risky (if you think owning US Treasuries are risky).

A Treasury bill matures in 1 year or less from when it was issued. A Treasury note is more than 1 year but up to and including 10 years. Treasury bonds are anything more than 10 years.

Is smart approximately the same as well connected? In that case the GOP congress seems very smart, putting in orders just minutes before whitehouse tariff announcments.