Saving with .rtf (or .RTF) extension only saves as .txt. All formatting is lost.
Opening a .rtf document (created in MS Word) which has the following text (with formatting):
WordRTF
looks like this in the editor:
{\rtf1\adeflang1025\ansi\ansicpg1252\uc1\adeff0\deff0\stshfdbch0\stshfloch0\stshfhich0\stshfbi0\deflang1033\deflangfe1033{\fonttbl{\f0\froman\fcharset0\fprq2{\*\panose 02020603050405020304}Times New Roman;}{\f1\fswiss\fcharset0\fprq2{\*\panose 020b0604020202020204}Arial;}
{\f168\fdecor\fcharset0\fprq2{\*\panose 04020705040a02060702}Algerian;}{\f236\froman\fcharset238\fprq2 Times New Roman CE;}{\f237\froman\fcharset204\fprq2 Times New Roman Cyr;}{\f239\froman\fcharset161\fprq2 Times New Roman Greek;}
{\f240\froman\fcharset162\fprq2 Times New Roman Tur;}{\f241\fbidi \froman\fcharset177\fprq2 Times New Roman (Hebrew);}{\f242\fbidi \froman\fcharset178\fprq2 Times New Roman (Arabic);}{\f243\froman\fcharset186\fprq2 Times New Roman Baltic;}
{\f244\froman\fcharset163\fprq2 Times New Roman (Vietnamese);}{\f246\fswiss\fcharset238\fprq2 Arial CE;}{\f247\fswiss\fcharset204\fprq2 Arial Cyr;}{\f249\fswiss\fcharset161\fprq2 Arial Greek;}{\f250\fswiss\fcharset162\fprq2 Arial Tur;}
{\f251\fbidi \fswiss\fcharset177\fprq2 Arial (Hebrew);}{\f252\fbidi \fswiss\fcharset178\fprq2 Arial (Arabic);}{\f253\fswiss\fcharset186\fprq2 Arial Baltic;}{\f254\fswiss\fcharset163\fprq2 Arial (Vietnamese);}}{\colortbl;\red0\green0\blue0;
\red0\green0\blue255;\red0\green255\blue255;\red0\green255\blue0;\red255\green0\blue255;\red255\green0\blue0;\red255\green255\blue0;\red255\green255\blue255;\red0\green0\blue128;\red0\green128\blue128;\red0\green128\blue0;\red128\green0\blue128;
\red128\green0\blue0;\red128\green128\blue0;\red128\green128\blue128;\red192\green192\blue192;}{\stylesheet{\ql \li0\ri0\widctlpar\wrapdefault\aspalpha\aspnum\faauto\adjustright\rin0\lin0\itap0 \rtlch\fcs1 \af0\afs24\alang1025 \ltrch\fcs0
\fs24\lang1033\langfe1033\cgrid\langnp1033\langfenp1033 \snext0 Normal;}{\s1\ql \li0\ri0\sb240\sa60\keepn\widctlpar\wrapdefault\aspalpha\aspnum\faauto\outlinelevel0\adjustright\rin0\lin0\itap0 \rtlch\fcs1 \ab\af1\afs32\alang1025 \ltrch\fcs0
\b\f1\fs32\lang1033\langfe1033\kerning32\cgrid\langnp1033\langfenp1033 \sbasedon0 \snext0 \slink15 \styrsid16329431 heading 1;}{\*\cs10 \additive \ssemihidden Default Paragraph Font;}{\*
\ts11\tsrowd\trftsWidthB3\trpaddl108\trpaddr108\trpaddfl3\trpaddft3\trpaddfb3\trpaddfr3\trcbpat1\trcfpat1\tblind0\tblindtype3\tscellwidthfts0\tsvertalt\tsbrdrt\tsbrdrl\tsbrdrb\tsbrdrr\tsbrdrdgl\tsbrdrdgr\tsbrdrh\tsbrdrv
... and so on ...
the rtf file I tried to open in Lexi