What are opioids? What’s the general mechanism of action of opioids? What are the use & benefits of opioids?Discuss

What are opioids? What’s the general mechanism of action of opioids?
What are the use & benefits of opioids?
Disadvantages of opioids/ side effects? nausea, vomiting, constipation, pruritus, dizziness, dry mouth and sedation. Side effects are extremely common with opioid therapy.
Explain the importance of opioid auditing?