How much is a change fee on Delta?

Excuse me, I'm curious about the change fee policy with Delta Airlines. Could you please elaborate on how much they typically charge for making a change to an existing reservation? Is there a standard fee across all ticket types, or does it vary depending on the type of ticket or the route being traveled? Also, are there any circumstances where the change fee might be waived or reduced? Thank you for your help in clarifying this matter.