I am failing to understand the bond ETFs.

I somewhat understand stock ETFs: ETFs own stocks, I buy a part of ETF, therefore, I also indirectly own stocks. When I sell my share of ETF, the ETF gets the cash by selling the shares it owns. Is this the right thinking?

How does this work for bond ETFs? Bond ETF owns government bonds, which cannot be sold at any time? If it's a 20-year bond, can it be sold before? For what price?

So, how do the bond ETFs work?

I am failing to understand the bond ETFs.

I somewhat understand stock ETFs: ETFs own stocks, I buy a part of ETF, therefore, I also indirectly own stocks. When I sell my share of ETF, the ETF gets the cash by selling the shares it owns. Is this the right thinking?

How does this work for bond ETFs? Bond ETF owns government bonds, which cannot be sold at any time? If it's a 20-year bond, can it be sold before? For what price?

How do the bond ETFs work?