Treo is a brand of handheld devices that was popular in the early 2000s, primarily known for its personal digital assistants (PDAs) and smartphones. These devices combined features like a calendar, address book, and email, making them useful for both personal and professional tasks. Treo devices often ran on the Palm OS, which was known for its user-friendly interface. The Treo line was developed by Palm, Inc., a company that played a significant role in the evolution of mobile technology. The devices were notable for their compact design and physical keyboard, which appealed to users who preferred tactile input over touchscreens. Treo's influence can still be seen in modern smartphones today.