When you give feedback, it means you offer a helpful response to someone's work or idea.
If you were recording your first album and you asked friends for feedback on which songs to include, you'd be asking them to offer their critical opinions on your music. Feedback is almost always offered or requested with the intention of improving the final product. Another meaning of feedback is a kind of sound distortion from an amplifier or microphone. This sense of electronic feedback has been around since about 1920, while the "critical response" definition didn't come into use until 1955.