Autocorrect is kind of a love/hate thing no matter what platform you use it on. In Windows 10, it works much the same as on other platforms, automatically replacing misspelled words if they are in the dictionary and applying a red underline if the word isn’t found at all.
The trouble is, Autocorrect’s usefulness in Windows 10 really depends on what kind of device you’re using. Though it sometimes claims to be a system-wide feature, Windows 10’s Autocorrect doesn’t show up everywhere. It works in some universal apps (especially built-in apps like Edge and popular apps like Facebook), but not in others. It’s up to app developers whether they want to use the Windows Spell Checking API or not. Autocorrect doesn’t work on most traditional desktop apps at all. It can even interfere with other spellchecker apps or services you might have installed, such as Spell Check Anywhere or Grammarly.