Structural isomers are compounds that have the same molecular formula but differ in the arrangement of their atoms. This variation in structure can lead to different physical and chemical properties, even though the number and type of atoms remain constant. For example, C4H10 can exist as both butane and isobutane, which have distinct structures. These isomers can be categorized into different types, such as chain isomers and position isomers. Chain isomers differ in the branching of the carbon skeleton, while position isomers have the same carbon skeleton but differ in the location of functional groups. Understanding structural isomers is essential in fields like organic chemistry and pharmaceuticals.