Difference between Mesh, nested arrays and terrain

I’ve been on Google for the past few hours and have come across a wide variety of solutions. Some utilize unity Terrain objects, some use Mesh and others maintain their own nested array index. I’d like to gain a deeper understanding of the differences between these methods of generating a grid/terrain.

My end-game objective is to be able to generate a 3D terrain that can be generated on-demand as a user explores new area. I’m completely new to Unity so I don’t want to build a foundation that’ll screw me later.

it depends on the platform u want to make the game for , u did not mention that ;

if that’s for android u should go with “Mesh” solution cause its faster but it does not look nice just like what unity terrain can be ,

and for Heavy platforms like pc and others u can choose terrain system or any other awsome plugins in asset store:)