Some substrates come pre-packed with nutrients, like the ADA product, or homemade MTS. Some are completely inert, and are generally cheaper. Sand and small gravel types make it easy for plants to root, and you can somewhat offset the lack of nutrients by adding root fertilizers. Some, like Flourite, are clay-based and inert, but are good at soaking up nutrients.
Be aware that something like Aquasoil will be "used up" in a matter of a year or two, and will continue to be good substrates, but will no longer release nutrients.