Final answer:
A Local Area Network (LAN) is an environment where computers are physically connected, allowing for high-speed data transfer over short distances typically within a single building.
Step-by-step explanation:
An environment where all computers are physically attached to each other and data is transmitted at high speeds over short distances is called a Local Area Network (LAN). This type of network is typically used within a single building or a closely situated group of buildings. A LAN allows computers and devices within the same local area to exchange data and share resources such as printers or file storage quickly and efficiently due to the high data transfer speeds and low latency inherent in short-distance communication.