A more thorough explanation:

Senior lien refers to a type of security interest in an investment that gets paid back before other liens. This means that if the debtor becomes insolvent, the senior lien holders get paid first, and the other lien holders get paid later.

For example, let's say a company takes out a loan and uses its property as collateral. The lender who issued the first lien on the property is considered the senior lien holder. If the company defaults on the loan, the senior lien holder gets paid back before any other lien holders.

It's important to note that there can be multiple senior liens, and there can be multiple tiers of liens. This means that one lien may be "more" senior than another but not the most senior lien.

Bankruptcy laws may automatically treat first liens as senior or may require specific contractual clauses to be negotiated stating that a lien ranks senior to later liens on the property. Virtually all liens contain these clauses and often add a requirement that the debtor receive approval before giving other investors liens on the property. Bankruptcy laws typically uphold these clauses.

Overall, senior liens provide a level of security for investors and lenders, as they ensure that they will be paid back before other parties in the event of insolvency.