One of the most common types of financial statements is the net worth statement for an individual, or a balance sheet if the subject is a business. In both cases, the assets are listed and totaled, liabilities are listed and totaled, and the liabilities are subtracted from assets, providing the bottom line, or what an individual or business is worth. This number can be negative.
In the broadest sense, an asset is anything of value and its worth is what you paid for it. A liability is anything of negative value, such as debt, and its (negative) worth is what you expect to pay to get rid of it.