Answer:
The high islands have higher topography and volcanoes, while the low islands are flat and just a few meters above sea level.
Step-by-step explanation:
Oceania's islands, by topography, can be divided into high islands and low islands. While it may seem too simple of a division, it is actually not, because there is a great difference in the islands' topography, and islands that would fall in the middle are simply lacking. What can be noticed is that the high islands lie along active tectonic boundaries, while the low islands are further away from tectonic boundaries.
The high islands have a common characterisitc in that that they all have active volcanoes, which are also the reason that they exist. Because the volcanoes are active, there is new lava pilling up regularly, so the islands keep their higher elevation. The low islands are remnants of volcanoes that existed millions of years ago. As the volcanic activity stopped, the erosion started to gradually lower them down, so much so that they are with maximum elevations of just a few meters above sea level. These islands will actually disappear in the very near future because of the rising sea levels.