Carbon allotropes are different forms of carbon that have distinct physical and chemical properties due to variations in their atomic structure. The most common allotropes include diamond, graphite, and fullerenes. In diamond, each carbon atom is bonded to four others in a three-dimensional structure, making it extremely hard. In contrast, graphite consists of layers of carbon atoms arranged in sheets, allowing them to slide over each other, which gives it lubricating properties. Other notable allotropes include graphene, a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice, and carbon nanotubes, which are cylindrical structures with unique strength and electrical properties. These allotropes have various applications in materials science, electronics, and nanotechnology, showcasing the versatility of carbon in different forms.