Island Points are a secondary sorting method for Island Top. The main goal is to differentiate islands that are at the same level. For example, if multiple islands are on island level 44 then their island rank will be determined by their Island Points. The Island with a higher amount of points will be on top of the other level 44 islands. Island level 45s will still be on top of any level 44s regardless of their point values. You should always consider building your Island Point value so you will not be overrun by other islands that are the same level as you. Once Islands max out at level 45, the only way to change positions on island top will be by their island points. Trophies are the main source of points, and can be purchased in the BM Shops. It's recommended to grind for trophies at the same time you grind levels so you don't get left behind!
Island Points are obtained by placing Spawners and Black Market Trophies. Each spawner tier has a different point value associated with it and Each tier of BM Shop has a Trophy you can purchase: Slime, Noteblock, Dragon Trophies. Point breakdowns can be viewed by clicking the beacon in /is points or using the /see points command.