It's quite common for someone to execute a deed, or make a will, leaving money or property in liferent to someone, and in fee to someone else. For example John Smith leaves his estate to his widow in liferent, and to his son in fee. Or John Smith buys a property and executes a deed giving his wife the liferent and his son the fee.
The liferenter is entitled to occupy the property, or to receive the income from the estate, until (s)he dies.
The son is the fiar.
So a fiar only gets legal title to the estate or property once the liferenter dies. And no, the fiar does not hold anything, or enjoy any benefits, until that time.