Other definitions of debt to equity may not respect this accounting identity, and should be carefully compared.
Generally speaking, a high ratio may indicate that the company is much resourced with (outside) borrowing as compared to funding from shareholders.
However, the ratio can be more discerning as to what is actually a borrowing, as opposed to other types of obligations that might exist on the balance sheet under the liabilities section.
In other words, actual borrowings like bank loans and interest-bearing debt securities are used, as opposed to the broadly inclusive category of total liabilities which, in addition to debt-labelled accounts, can include accrual accounts like unearned revenue.
On a balance sheet, the formal definition is that debt (liabilities) plus equity equals assets, or any equivalent reformulation.