what kind of product is?

Mainframe computers are computers used primarily by corporate and governmental organizations for critical applications. The term originally referred to the large cabinets that housed the central processing unit and main memory of early computers. Later, the term was used to distinguish high-end commercial machines from less powerful units. Most large-scale computer system architectures were established in the 1960, but continue to evolve.

what is an useful product?

Mainframe computers are useful for bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and transaction processing.

What do you use it for?

I do use Mainframe computers in my work for resource computing planning, and data processing.

Some advantages and disadvantages about the product?

Main Advantages:

• High-level computing: One of the main characteristics of mainframe computers is their ability to process data and run applications at high speeds. 
• Increased processing power: Mainframe computers are supported by large numbers of high-power processors. 
• Virtualization: A mainframe system can be divided into logical partitions. 
• Reliability, availability, and serviceability.
• Mainframe systems are reliable because they can detect, report, and self-recover from system problems. 
• The serviceability of mainframes means they make it relatively easy to detect and diagnose problems, making it easy to fix problems in a short time and with little downtime.
• Security: As mainframes are designed specifically for large organizations where the confidentiality of data is critical, mainframe computers have extensive capabilities for securely storing and protecting data. 
• Long lasting performance: Mainframe computers are known for their long-lasting performance. 

Main Disadvantages:

• One of the prominent drawbacks of mainframes is their cost. Hardware and software for mainframes are clearly expensive. 
• Secondly, mainframe hardware occupies more space than other computers. 
• Finally, one needs high-end skills to work with mainframe computers.