Whereas an eternal law has no end, a finite law does. There are many commands in Torah that Hashem has given, which are meant only for a particular period of time.
For example, when G-d told Abraham to slay Isaac, that was a unique command. It was not given to all of G-d’s people, and it is not a standing order for fathers to slay their sons. Another instance of a finite command was when Moses made the fiery serpent and set it on the standard, and whoever looked at it would live. That was not something that regularly happened in the days of Moses and throughout the history of Israel – it was a unique command never to be duplicated.
And so now we have discussed the two categories of law, in regards to duration. All laws are either eternal or finite. There is no third option. A law, once it is given, either lasts forever, or it ceases at a certain point in time.