Profit is sales price - cost - expenses. So yes, if you bought something for $1000 and sold it for $1,100 your profit is $100, assuming no transaction fees.
It is irrelevant if you are buying and selling bonds, trading cards, or broomsticks.
Because the price will change to so that the yield is "fair" (according to market expectations) and people want to use their money for other things now rather than waiting for the next auction.
On the day of a 2 year note auction, for example, if you hold a 5 year note that was issued 3 years ago (so it has 2 remaining years), the value of your 5 ...
Bonds are not traded on an exchange like stocks, and so there are no "designated" market makers like for stocks, but there are some brokers that will buy and re-sell bonds to keep liquidity up (and to make a bit of profit for themselves).
So I wouldn't expect your bond trade to be executed in "seconds" but if there are buy and sell quotes ...
You have to dig into the story to get the details. The headline or the opening sentences will generally not tell you.
I found this headline from [October 15th 2021]:
Treasury yields gain after retail sales increase in September
It stories 2nd paragraph said
The yield on the benchmark 10-year Treasury note climbed by 5.3 basis
points to 1.572% at 4:10 p.m. ...
If treasuries are at 2% then 2% is the risk-free rate of return. If you are a risk-adverse investor or if you want to allocate some percentage of your portfolio to low-risk assets either permanently or temporarily while you look for a better place to invest it, you'd want to hold some quantity of risk-free assets like treasury bonds.
If you're a 30 year old ...
Do they refer to the most recently auctioned note only?
Yes - the most recently issued bonds are called "on-the-run" and are typically used to quote current yields. Bonds issued before the most recent auction are called "off-the-run" and are still traded but are not as liquid as on-the-run.
and so this will affect the price of the ...