Treasury notes

I think what you're actually wanting to look at is called treasury strips or zero coupon bonds. They're usually bought at deep discount and mature at par value, the owner would pay a phantom income tax however.

These are kinda an old way of funding a specific goal for something in the future with a lump sum. But since you mentioned your adding to this monthly, you may wanna check out some different investments within a UGMA/UTMA or 529 account. Depending on what you specifically want the money to do.

T-Bills, T-Notes, T-Bonds are the same. They refer to different time intervals.

Savings Bonds are different from above and different depending on the series purchased.

They are exempt from stat income tax but you have to pay federal.

You can purchase directly from the Treasury at Treasury Direct or you can open an account with a brokerage which may or may not charge you commission for purchasing these in your account.

Obviously, do your own due diligence with respect to where you should be in the yield curve.

I recently read up on Series I and Series EE savings bonds.

Series I is attractive because it locks in your real rate of return. The problem is that real rate of return is currently 0.00%. I wouldn't buy as-is. If the real interest portion of the Series I savings bond ever returns to something attractive, I plan to purchase aggressively. You're limited to $10,000 in purchases per SSN per year.

Series EE is attractive because it, at a minimum, doubles the face value at 20 years which is a 3.50% or so rate of return (compared to the 20 Year T-Bond at 2.85%). It also doesn't have the price risk. It obviously has inflation and liquidity risk. You're limited to $10,000 in purchases per SSN per year.

High yield CDs are 1.70% to 1.90% for 5 year terms. You can start a ladder which would be able to take advantage of rising rates (if it comes to fruition).