Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation.
Anti-inflammatory drugs make up one half of analgesics, remedying pain by reducing inflammation as opposed to opiates, which exert their pain-killing abilities by directly binding to opiate receptors in the brain.
Steroidal Anti-Inflammatory Drugs
Many steroids—specifically glucocorticoids—reduce inflammation by binding to cortisol receptors. These drugs are often referred to as corticosteroids, though that is a larger category.
Non-Steroidal Anti-Inflammatory Drugs
Non-steroidal anti-inflammatory drugs (NSAIDs) alleviate pain by counteracting the cyclooxygenase (COX) enzyme. On its own COX enzyme synthesizes prostaglandins, creating inflammation. In whole the NSAIDs prevent the prostaglandins from ever being synthesized, reducing or eliminating the pain.
In addition to medical drugs, many herbs have anti-inflammatory qualities, including: hyssop, Arnica montana (that contains helenalin, a sesquiterpene lactone), and willow bark (the latter of which contains salicylic acid, which is related to the active ingredient in aspirin).
On the other hand, there are analgesics like acetaminophen (paracetamol outside the U.S., commonly sold as Tylenol) which are commonly associated with anti-inflammatory drugs, but which have no anti-inflammatory effects.
Icing tissue injuries has an anti-inflammatory effect and is often suggested as an injury treatment and pain management technique for athletes.