In virtually every role-playing game two different types can be differentiated:
These (I couldn't think of a better name to describe it) are the ones that you'll normally have to deal with. They form those creatures of which you can and will usually find a plethora during your journey. Their strenth is rather moderate and you should be able to defeat them without any troubles. This way you can earn some good experience points and coins, which raise your levels and allow you to buy something. Furthermore they can nearly always leave items behind. Watch out for enemies that can even drop some really strong artefacts!
Usually the bigger guys. They're the ones who you'lll only be able to encounter once during your journey, they usually await innocent wanderers like you near the end of some areas. Their power are astonishingly great, and to defeat is vastly more difficult than the normal little quarrel. Strategic planning with sword and sorcery is in most cases a must to be able to defeat them! But it pays: After a battle's over you'll not only get tons of level experience and gold, but a nice and rare item as well!