A "block" is a solid piece of material, often rectangular or cubic in shape, used in construction, manufacturing, or various crafts. Blocks can be made from different materials, such as wood, concrete, or plastic, and serve various purposes, including building structures, creating art, or providing support in various applications. In the context of computer science, a "block" refers to a unit of data or a segment of code. For example, in blockchain technology, a block contains a list of transactions and is linked to previous blocks, forming a secure and immutable chain. This structure is fundamental to cryptocurrencies like Bitcoin and ensures data integrity.