The "X series" refers to a line of products or models that typically share a common design or functionality, often produced by a specific company. These series can include various types of technology, such as smartphones, laptops, or gaming consoles, and are designed to cater to different user needs while maintaining a cohesive brand identity. In the context of smartphones, the "X series" may feature advanced camera systems, high-performance processors, and sleek designs. Companies like Apple and Samsung have their own versions of the X series, which are popular among consumers for their innovative features and reliability.