A cell phone/smart phone, or tablet.

Typically, website users are said to be desktop visitors, or mobile visitors.

Mobile users arrive at a website on a mobile device, like a smart phone, or tablet, and are often on the go, commuting in transit, at a coffee shop, or out and about on their phone.

In contrast, desktop users tend to be at home or work on the personal computer.

Looking at users by device type can be valuable for providing insight into how users behave on your website.