How do you Use layers in Adobe Photoshop?

Answer 1

if you imagine each layer as a sheet of paper and the more layers the more complex the picture is

because if you might make a mistake layers are good because you can just delete the layer. also if you want to use any effects very often you only want to apply it to one layer and if you don't you can select more than one layer. layers are also useful when creating something it can sometimes be easier to add the background last, and layers lets you simply 'place' it beneath the foreground