AAA level: the highest financial guarantee, the highest security and the strongest ability to perform insurance contracts.
AA: It has good financial security, and it is not much different from AAA in the ability to perform insurance contracts.
A: It has good financial security, but compared with high-grade insurance, its ability to perform insurance contracts is easily affected by unfavorable economic conditions or changes in the insurance environment.
BBB: Financial security is average, but compared with high-grade insurance, its ability to perform insurance contracts is more easily affected by changes in unfavorable economic conditions or changes in insurance environment.
BB: Financial security is guaranteed to some extent, but unfavorable economic conditions or changes in the insurance environment will often weaken its ability to perform insurance contracts, which is unsafe in the long run.
B: At present, the insurance contract can be performed, but it will be unreliable under unfavorable economic conditions or insurance environment.
CCC: vulnerable to adverse economic conditions or changes in the insurance environment, its ability to continuously perform insurance contracts is unreliable unless there is a favorable economic environment.
CC and C: CC or C insurance can't fully fulfill the insurance contract and is in danger of bankruptcy.
D: in bankruptcy.
Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.