The health factor is a numeric representation of the safety of your deposited assets against the borrowed assets and their underlying value. The higher the value is, the safer your funds are from being liquidated.
A multiplier represents the liquidation threshold. For example, HealthFactor of 0.9 means that if the amount you borrow is worth (at least) 0.9 of your collateral, your position is subject to liquidation. Must follow: CollateralFactor <= HealthFactor< 1.