This nozzle is a high temperature Adventurer series nozzle. It is suited for ABS, PETG and PC but it will also work with lower temperatures required for PLA (although Flashforge recommend using the lower temperature 240℃ nozzles for PLA). The larger 0.6mm means you can print faster (more plastic output) and also means that you are less likely to get a clogged extruder if you used an impregnated material.
The adventurer nozzles are very easy to replace. Simply press the quick release buttons to remove the old one and then insert your new Flashforge adventurer nozzle