Developer website: Silver Software
Select some text in any application and call contextual menu for selection (Ctrl-click). In Text Correction submenu select desired operation. If application supports Apple Events Model then selected text will be replaced with result of correction. If text cannot be replaced 'in fly' (you will hear system alert sound in that case), that means application you are using does not support Apple Events Model. But you still can use Text Corrector, because correction result is stored in Clipboard as well, so you can use Command-V and paste it anywhere you want.