Manual

Eraser Tool

Eraser Tool properties are similar to Brush Tool.
hotkey: E
More on Brush Tool here
Spree
Erasing layer content with Eraser Tool - the erase effect first goes onto a Spree layer.
Pressing X key will toggle spree erase mode and you will be able to un-erase back the content you just erased with Eraser Tool.
More on Spree here