To open eraser settings:

1. Select eraser tool from toolbar.
2. Tap on the eraser tool once more.

When "Erase entire object" is enabled, an entire object (e.g., an entire stroke) will be erased.

When "Erase locked objects" is enabled, locked objects will become erasable.

You can also adjust the types of objects that can be erased, by default only Pen and Highlighter blocks are erasable.