We tend to use basil as a garnish that is minty, zesty, peppery and with some intense clove like notes. Refreshing and intense in flavor a little goes a long way. Oregano is more often cooked with a dish to develop the flavor and it is earthy, herbaceous, woody and pungent with mint to citrus notes.
Gremolata is a traditional Italian ‘sauce’ with parsley, garlic and lemon zest. No other ingredients are required and you can see that this means it is more of a garnish than a sauce. It has evolved to include a little bit of lemon juice and even olive oil, however this moves into more of a pesto.
Parsley is a useful biennial that will grow outdoors in colder climates and basil being a tender annual. Both can be used in cooking with slightly different taste profiles and history of culinary uses. Nutritionally both of these herbs are loaded with vitamins and minerals as well.
Pesto is nutty and often has a hard cheese added, using olive oil. Salsa Verde has an element of brine with capers or anchovies and also a small amount of vinegar added. Chimichurri has vinegar and chilies added. The leafy herbs can vary as can the consistency and where they are used.
When looking at cut and come again we have Evergreen and Herbaceous herbs to take into account. The evergreen type will take a good prune and harvest through the growing season, with a general trim before the dormant Winter. Herbaceous herbs will thrive with regular pinching out of new growth.
By categorizing the flavor profiles of herbs and spices it is easier to understand how they may match one another, or more importantly how they may compete and overpower other flavors. You do not want to waste delicate flavors of saffron by pairing with fresh ginger, for example.