How safe arer bonds is a pretty general question? It depends not only on who is issuing it but the seniority of the debt and the terms.
I think you will find that everyone is concerned with safety and return. Does risk/return ring a bell?
Basically with bonds, the higher the coupon the higher the risk.
Bonds are only as secure as the company backing them. Essentially you are lending money to the company in return for a coupon (interest). If the company goes bust, normally all it's assets ae sold in order to pay off the debt holders (including bond holderrs). If after this anything is left over, finally shareholders are paid. For this reason buying bonds is less risky than buying shares in a company.
As for bonds vs savings account. A savings account is generally quite liquid but is based on a rate over a quite short term (normally <2 years). After the original deposit term rate ends, the rate will cange. Bonds are generally much less liquid and are over a longer term. You are normally compensated with a higher interest rate for locking in your money for longer.