A lien is a legal claim to an item of property. When you get a mortgage to buy a home, your lender uses the home as collateral. To do this, they place a lien on your home; this is called the first lien, the first mortgage lien, or the primary lien. If you fall behind on your loan payments and default on your mortgage, your lender has the right to repossess the home, sell it, and use the proceeds to pay off your debt.
If there is more than one lien on the home, the proceeds of the home sale will pay off the first lien holder first, the second lien holder second, and so on.
Better Mortgage only offers first-lien mortgages and debt consolidation mortgage refinances. So, if you have a second mortgage, you are unable to refinance it through Better Mortgage unless you consolidate it, or subordinate it. In other words, Better Mortgage cannot solely refinance a home equity loan (HEL), a home equity line of credit (HELOC), or a piggyback loan agreement/note.