>>21434545
In the US bonds are loosely separated into municipal (state and local), treasury-backed (federal), and corporate. The original holders can sell them on the secondary markets to other entities similar to stocks. Although the bond market tends to be (a) much larger allotments than stocks and (b) less fluid on a day-to-day basis. Bonds are typically valued in deflationary environments because of their fixed returns (annual and to maturity). They return less than stocks but that is because the downside risk is much smaller. As long as the entity who owns the bond can pay its debts, a low bar, you cannot lose money on the investment (if you are adjust for inflation you might if the returns are too low). Corporate bonds that default usually mean the stock has imploded too. In most bankruptcy proceedings, bondholders are compensated first (cents on the dollar) before equity (stock) holders.
The main practical advantages between the three categories is return/risk and tax treatment. Corporate bonds have highest returns but most businesses over time eventually go bankrupt. Municipal bonds have slightly less with slightly less risk of default if picked carefully but the main advantage is that the capital returns are frequently exempted from local and state taxes, especially if you live there. Federal bonds are the same for the federal level and have the lowest risk of all but the lowest returns. International bonds will likely not have these tax privileges for where you live. ETFs sourced from one of your country's stock exchanges might be a good way to get this kind of exposure and not get hit with multiple taxes (foreign and local).
Uncertainty is very high and fears of deflation have made the premiums on good bonds absurd and junk bonds basically price controlled by central banks. This is mainly because bonds protect the nominal value of your wealth (a preoccupation of wealthy conservative investors).