I think the posts so far are confusing two separate things: the concept of usufruct, and succession rights. The usufruct is a type of property right in the civil law system, which anyone can use. It may have a particularly common application in estate planning, because it fits nicely into the common desire to let the surviving spouse continue in the house/farm until death, when it then passes to the children, but it doesn’t have to be used solely for family matters and succession planning.
Suppose Farmer A has two plots of land and needs money for new machinery and improvements. He could sell the usufruct in one plot of land to Farmer B for a set period of time, and use the money to buy his machinery and improvements. Farmer B is on the second plot and can farm it, until the term of the usufruct is up, and then Farmer A regains control over it.
The idea of a usufruct comes from the Roman civil law conception of property. In civil law theory, there are three aspects of the right of property: the usus, the fructus, and the abusus. Usus is the right to use the property; frucutus is the right to take the fruits of the property; abusus is the right to alienate or alter the property. Usufruct combines the rights of usus and fructus in one person, while another person keeps the abusus.
English common law never adopted this conception of property. Common law property law has its roots in the feudal law of tenure of estates. You can achieve similar results to the civil law types of property, but the theoretical basis is different.
The difference between these property rights and the succession principles mentioned upthread is that when these property rights are used in estate planning, the surviving spouse (or whoever the testator wants to have the immediate possession, like a brother or sister) gains the right of staying on the land, whether by a usufruct in civil law, or by a life interest in common law. The other heirs have no right to the land until the death of that person.
By contrast, under the succession / intestacy laws, all of the heirs, both the surviving spouse and the children, usually have an immediate percentage interest in the assets of the estate. If they can’t reach an agreement on how the estate will be treated, any one of the heirs normally has the right to require that the estate be wound up and the proceeds divided immediately according to the percentages set out in the succession or intestacy laws.
The profit à prendre in English law is not quite as strong as a usufruct, although it is similar. It normally gives the person the right to enter on the land and take a particular fruit from the land, so under the civil law conception it would have a sliver of usus (the right to enter) and a sliver of fructus ( the right to take whatever fruit is granted - apples, or coneys, or whatever).
The life estate is perhaps closest to the usufruct. And yes, the “remainder” would be the equivalent of the person holding the abusus right to the land covered by the usufruct, although there are technical differences between the two. The person holding the right of remainder is called the remainderman.
None of the above is intended as legal advice, of course. I’m running on empty from long-ago common law and civil law classes.