A portable power station is essentially a big rechargeable battery that you carry around. Deplete it and it's useless until you can recharge.  A generator, by definition is a device which actually will convert some type of energy to usable electricity in whatever circuitry you have it connected to. Examples of this would be gas generators -- commonly used as power sources for remote areas or as whole-home backups, electric generators -- not very common, but they convert some type of mechanical action to electricity and solar generators which can use solar panels to power devices or homes, often using a battery to temporarily store the electricity. These batteries are often portable power stations themselves.