This is the official manual for the latest Org-mode release.
Just like in LaTeX, ‘^’ and ‘_’ are used to indicate super- and subscripts. Again, these can be used without embedding them in math-mode delimiters. To increase the readability of ASCII text, it is not necessary (but OK) to surround multi-character sub- and superscripts with curly braces. For example
The mass of the sun is M_sun = 1.989 x 10^30 kg. The radius of
the sun is R_{sun} = 6.96 x 10^8 m.
To avoid interpretation as raised or lowered text, you can quote ‘^’ and
‘_’ with a backslash: ‘\^’ and ‘\_’. If you write a text
where the underscore is often used in a different context, Org's convention
to always interpret these as subscripts can get in your way. Configure the
variable org-use-sub-superscripts to change this convention. For
example, when setting this variable to {}, ‘a_b’ will not be
interpreted as a subscript, but ‘a_{b}’ will.