To optimize a client’s campaign to get the most out of her mobile advertising, you can:
set shorter conversion windows to capture users who convert after researching on multiple devices
set a mobile bid adjustment for the campaign based on insights from estimated cross-device conversion and total estimated conversion data
edit the campaign’s ad text to include information about how customers can purchase her product on their computers
use the maximize clicks flexible bidding strategy to increase the number of clicks her ads get from users viewing her ads on mobile devices
To alter your bids when your ads appear on desktops, tablets, and mobile devices, you can specify a desktop, tablet, or mobile bid adjustment at the campaign level or at the ad group level. If you set a device bid adjustment at the campaign level and at the ad group level in a single campaign, the ad group device bid adjustment is used when determining your bid. However, if the campaign device bid adjustment is -100%, then the ad group device bid adjustment isn’t used.
Just as with desktop AdWords campaigns, mobile campaigns use bidding and targeting to determine where and when your ad shows up. Sometimes a click is worth more to you if it comes from a mobile device, at a certain time of the day or from specific locations. By setting bid adjustments, you can increase or decrease your bids to gain more control over when and where your ad is shown.
Read more here: https://support.google.com/partners/answer/6209121?hl=en-GB