About device targeting
For Display and Video campaigns, you can target specific device types, operating systems, device models and ad inventory (spaces where publishers allow ads to run), as well as operators and wireless networks. Some of these advanced mobile and tablet options aren’t available for other campaign types.
Say that you sell accessories for mobile phones and you want to show your ads to people who own a Mobile Device X. With device model targeting, you can create a message in your ad that's a lot more focused: "Customised Cases for Mobile Device X".
Setting device targeting
You can set targeted bid adjustments for tablets, mobile phones and desktop computers. In the previous AdWords experience, you can set your ads to target specific devices and ad space under "Settings" in the "Devices" section. In the new Google Ads experience, you can set your ads to target specific devices and ad space by clicking Devices in the page menu. Determine which Google Ads experience you're using.
Computers: These are desktop or laptop devices with screens larger than 7" in diagonal. Selecting this option will give you access to all ad inventory that runs on computers.
Mobile: These are hand-held devices that include a phone.
Tablet: Tablets are mobile devices that don't necessarily include a phone.
TV screens: These are devices that stream TV content such as smart TVs, gaming consoles and connected devices like Chromecast. This targeting option is only available for Display and Video campaigns.