Can someone give me a definition of "key internal control" as opposed to just an internal control?

Answer 1

Further to my earlier answer, you might be interested in the following links:
1st link - Key Internal Control Activities
2nd link - If you're studying internal control, you should familiarise yourself with The Committee of Sponsoring Organizations of the Treadway Commission (COSO)'s framework. COSO states that internal control consists of five interrelated components:
1. Control Environment
2. Risk Assessment
3. Control Activities
4. Information and Communication
5. Monitoring

3rd link - The New Compliance Background
Although the SEC has not yet issued a definition or framework for internal controls, it is expected to closely align with the key internal control concepts of the Committee of Sponsoring Organizations of the Treadway Commission (COSO).