You can read about it in detail here:

https://splinterlands.gitbook.io/the-secret-of-praetoria/production-points/production-points

Really it just means that different cards will produce different resources while working on land.  Gold Foil cards will produce more than regular cards, Alpha cards will produce more than Chaos Legion cards. 

Production Points won't matter when playing the game... and probably won't matter when renting cards (or renting out cards) in the short term... but I do think buying and selling cards will take Production Points into consideration as people will want older or gold foil cards to work their lands.