It has two healthful aspects, said Paul Vossen, olive oil specialist for the state of California. It's monounsaturated, "which is the best type of fat for our bodies," he noted, and it contains antioxidants and polyphenols, which are believed to protect against cell damage. (Pungency and bitterness, both considered attributes in olive oil, indicate the presence of polyphenols.)

Fruity, bitter and pungent are positive attributes in olive oil. Even the best olive oils can taste very different from one another, depending on the olive variety, fruit maturity, growing region and extraction technique.

Oil made from ripe olives is less bitter and pungent, and the bitterness of oil made from less-ripe olives mellows a bit with time.

Very bland olive oil can be an indication that it is chemically extracted.

Heat destroys some of the flavor and some of the benefits (polyphenols) of olive oil, so really fine olive oil "should be thought of as a condiment, a spice, to flavor your food," Vossen said. But olive oil remains a better choice for cooking as well because it's monounsaturated.

Here are some of the more common labeling terms for standards and grades of olive oil:

Extra-virgin olive oil: This oil contains no more than 0.8 percent acidity, is processed without chemicals, and is judged by trained testers to have zero defects and superior taste. This is the highest quality rating for an olive oil.

Virgin olive oil: This oil has an acidity of less than 2 percent, is processed without chemicals, and judged to have a good taste and possibly some defect. It cannot contain any refined oil (chemically extracted). It is slightly lower quality than extra-virgin olive oil.

Pure olive oil: Oils labeled as pure olive oil or olive oil are usually a blend of refined olive oil and extra-virgin or virgin olive oil.

Other terms that might appear on labels:

"100% Pure Olive Oil" is often the lowest quality available in a retail store. Better grades would have "virgin" on the label.

"Light olive oil" is actually refined olive oil. It does not have lower fat content. All olive oils have 120 calories per tablespoon.

"Bottled in Italy" or "Packed in Italy" does not necessarily mean that the olive oil originated in Italy. Labels might indicate the origin of the olive oil, which often is a mixture of oils from several countries.

—Susan Taylor