A data center is a facility that houses servers and critical network systems to collect, store, process, and distribute massive amounts of data. Data centers provide 24/7 services to customers and ensure data security. They consist of servers, cooling systems, ventilation, security systems, power distribution and backup units, and redundant backup systems to maximize uptime. Data centers are classified based on their redundancy and availability, with Tier III centers having the highest availability of 99.995% due to redundant systems and dual power. There are different types of data centers including internet, cloud, and dark centers.