[X] When you check Backspace Unindents (the default) and the cursor is on a blank line or on the first non-blank character of a line, you can press the Backspace key to outdent the line.

Outdenting aligns the line to the previous indentation level.

[ ] If Backspace Unindents is not checked, the Backspace key merely moves the cursor to the left one character each time you press it.