All you mentioned are seasonings; things used that add to or affect the flavor of other foods, but which, usually, are not eaten by themselves.
Salt is unique. It is a mineral, and the only rock we eat by choice. As MissyJean implies, there is nothing else like it. Depending on quantities used, and point in the cooking process it is added, salt can either add it's own taste, or cause the primary foods to taste more like themselves.
Herbs are the soft aerial parts of plants----the leaves, flowers, sometimes stems, etc. Everything that grows above ground that isn't a seed, fruit, or other hard part. They are used either fresh or dried, and the form can have a distinct effect on the flavor. See basil as an example.
Spices are the hard parts of plants---the roots, seeds, buds, bark, fruit, pods, and so forth. They are almost always used in a cured form, primarily dried, but sometimes pickled.
Some plants provide both. The coriander plant, for instance. When the fresh leaves are used we call in cilantro. But the seeds, called coriander, are used as a spice.
There are other items used as seasonings as well. For instance, a squirt of lemon juice, as we all know, can often perk up an otherwise dull dish. I suppose it would, when used that way, technically be a spice. But nobody thinks of it that way.
Sometimes, too, vegetables that could be served on their own are used as seasonings. The famed mirepoix, for example, or anytime aromatics are used to perk up the flavors.