org-adapt-indentation is a variable defined in ‘org.el’.
Its value is t

Documentation:
Non-nil means adapt indentation to outline node level.

When this variable is set, Org assumes that you write outlines by
indenting text in each node to align with the headline (after the
stars).  The following issues are influenced by this variable:

- The indentation is increased by one space in a demotion
  command, and decreased by one in a promotion command.  However,
  in the latter case, if shifting some line in the entry body
  would alter document structure (e.g., insert a new headline),
  indentation is not changed at all.

- Property drawers and planning information is inserted indented
  when this variable is set.  When nil, they will not be indented.

- TAB indents a line relative to current level.  The lines below
  a headline will be indented when this variable is set.

Note that this is all about true indentation, by adding and
removing space characters.  See also ‘org-indent.el’ which does
level-dependent indentation in a virtual way, i.e. at display
time in Emacs.