Regression testing is when you run every test to check every bug fixed in the application to make sure you haven't reopened any bugs that were fixed in a previous version (a "regression").
What a correction release is ... my guess is that the previous version of the app was released after passing the current set of regression tests and it was found that the regression tests themselves had to be updated (because they were buggy in some way - they missed cases that should have been checked, for instance) - and the app failed the new tests in some way.
