Clicks: The number of Clicks generated by the campaign, delivering a visitor to the website
CTR: Click Through Rate, the percentage of people who Clicked an ad vs. saw an Impression.
CPC: Cost per Click, dictated by competition from other advertisers and or own maximum bids.
Impressions: The number of times Ads within the campaign have been shown.
Impression Share: The effective share of voice a Search campaign enjoys in a given market/region. Varies based on several factors, but primarily overall audience size and the budget available to reach it.
Time: Time spend on the website after Clicking on an Ad, measured in seconds. Higher Time on Site is generally indicative of a more engaged visitor - although there are cavaets to this (e.g. viewing a single page, regardless of time spent on it, will record 0 Time due to way Analytics functions).
Pageviews: The number of Pages viewed by a visitor after arriving at the website from an ad Click. More Pageviews general indicates a more engaged visitor, although there are caveats to this.
Conv/Conversions: tangible actions which take place on site after a user Clicks or Views (view-through) an ad. Typically e-commerce transactions or newsletter sign ups.