Do I have to retype information every time I make a mistake in SQLPlus If I make a mistake in SQLPlus while inputting an 'insert into' command, is there a way I can bring this information back up in order to edit it?
Several ways.

You can set the EDITOR environment variable before running SQL*Plus (Assuming Unix), to allow use of an external text editor (vi, by way of example):

export EDITOR=vi


Then type ed in SQL*Plus to edit the previous query in the vi editor. Of course, you may prefer nano, pico, emacs, vim etc etc.

If you don't wish to set an environment variable, you can add define _editor=vi to your $ORACLE_HOME/sqlplus/admin/glogin.sql file instead.

My favourite way of achieving SQL*Plus edit heaven (in Unix) is by using rlwrap. This adds readline support to SQL*Plus and allows you to easily edit within SQL*Plus itself.

Install rlwrap from your distributions package repository (or download &amp; compile from the website here), then add the following to your shells startup script (.bashrc/.bash_profile or similar):

alias sqlplus="rlwrap -i sqlplus"