A more thorough explanation:

singuli in solidum

When there are multiple people responsible for a debt or obligation, singuli in solidum means that each person is responsible for the entire amount, not just a portion of it. This is different from pro rata, where each person is only responsible for their own share of the debt.

Let's say that three friends rent an apartment together. They all sign the lease and agree to split the rent equally. If they are liable singuli in solidum, it means that if one friend doesn't pay their share of the rent, the other two friends are responsible for paying the entire amount. On the other hand, if they are liable pro rata, each friend is only responsible for their own portion of the rent.

Another example could be a business loan taken out by multiple partners. If they are liable singuli in solidum, each partner is responsible for paying back the entire loan amount. If they are liable pro rata, each partner is only responsible for paying back their own portion of the loan.

These examples illustrate the difference between singuli in solidum and pro rata. Singuli in solidum means that each person is responsible for the entire amount, while pro rata means that each person is only responsible for their own share.