Agave nectar is actually a syrup that its name does not suggest. It is made from the fluid from inside the blue agave plant. This plant is the same one used to make tequila and mezcal if you were wondering.
The plan itself grows in the Southwestern States and the northern part of South and Central America.
To make it, they extract the liquid. Then it is filtered before it is heated. The heating process distills its components down into a syrup-like consistency. In terms of the viscosity, it is a bit thinner than honey and has a more neutral sweetness.
This process is somewhat similar to how maple syrup is made. In fact, it comes in different color grades just as maple syrup does depend on the level of processing.
The light color is great for a subtle flavor. Use this for baking, sauces, beverages as it will not affect the flavor of what it is added to too greatly.
The amber which is a deeper color is wonderful for desserts, sauces, and savory dishes as it leans towards a darker sweetness in terms of flavor.
The dark agave nectar is deep brown in color and suitable for heavier sauces and dishes and desserts with more bold flavors.
Agave nectar tends to be a bit sweeter than regular granulated sugar causing you to use less in most cases and it has fewer calories than honey, which is why you see it so often in fruit bowls, in smoothies, etc.