Bonds pay a fixed return. You buy it and there is no question what the return is for the term of the bond. Bond funds on the other hand, buy and sell bonds in an attempt to do better but there is also risk of doing worse.
You buy a $1000 bond that pays 2 percent for 5 years. Great, that's what you get. A fund buys the same bond and then interest rates rise, so they sell the bond at a slight loss (vs $1000) so they can invest in something with a better return. It becomes a bit of a game and can lose or gain vs the fixed return of buying and holding actual bonds.
You buy a $1000 bond that pays 2 percent for 5 years. Great, that's what you get. A fund buys the same bond and then interest rates rise, so they sell the bond at a slight loss (vs $1000) so they can invest in something with a better return. It becomes a bit of a game and can lose or gain vs the fixed return of buying and holding actual bonds.