Seems to be a simple question to answer. In theory, when one holds a real estate, it means the land, the improvements to the land (structure), the space above and the minerals beneath the land.
In some cases, minerals rights might be owned by one or more individuals or a corporation. What this means is if there is oil below your property then the owner of such rights might be able to extract. This does not say the mineral right owner is going to place an oil rig and drill in the backyard. They have the right to use different drilling technologies to extract the mineral as they have right to the mineral ownership.
In many areas of Texas, developers have reserved the mineral right of the acres of land that they have developed, selling only the what is called the surface estate, i.e., land surface and the building structure to the buyer. When you are buying real property and wanted the mineral right to be conveyed, talk with your real estate agent.