Processing modes refer to the way a computer processes information. Computers either use single-threaded or multi-threaded processing.
Single-threaded processing means that the computer can only work on one task at a time. It's like a person who can only do one thing at a time.
Multi-threaded processing means that the computer can work on more than one task at a time. It's like a person who can do two or more things at once. This makes the computer much faster and more efficient.