Olive oil is considered a healthy oil and is high in unsaturated fat though all fats and oils are best eaten in moderation.  There are many different types of olive oil with different flavours. Many cooks and gourmet eaters consider extra virgin and virgin olive oil better than others.  Taste is a matter of personal preference.
When frying food in olive oil take care not to overheat it as overheating can make it unhealthy.  (See Frying in hot vegetable oil for more. This is from a different website that includes meat recipes.) Olive oil can be added to boiling water for soups and stews without risk of overheating. The oil can't get hotter than boiling water. Unfortunately the taste won't be the same as when boiling water is added after food is fried. This should work for some recipes but not others. To give dishes a Mediterranean flavour without any risk of overheating oil you can add olive oil to cooked pasta.