Is it true....if you put bark on top of the soil...

is it true... my friend said that if i put bark on top of the soild is gonna help the plant...but if it dose in what way dose it ???

yeah thats about it...the bark will absorb any heat from the light and work as a mild insulator keeping the soil more moist and a little bit cooler.

so would it be a good ideea to add bark or its ok the way it is ?