Unity render lag questions

Since the unity camera renders the stuff only what it sees,
if there was a huge terrain would the whole thing be loaded if only one side is being watched? and in that case would multiple pieces of the terrain be more efficient in fps terms?

thanks for your time, sincerely vultt3rim

It is always in memory. Unity performs optimizations by reducing triangles but this all noneffective in regards to large scale. Splitting and performing management on parts will be much more effective to memory and rendering performance.