The user viewed or clicked an ad. (Learn more about ads.)
When the ad is displayed, this counts as one Product Impression.
When the ad is clicked, this counts as one Product View.
When the ad is displayed, this has no effect on product analytics. (This does count as one Ad impression, but the Analytics Channels show Product Impressions; not Ad Impressions.)
When the ad is clicked, the Store Page is shown. All of the product thumbnails shown as a result count as Product Impressions that belong to the Ads channel.
If any of these thumbnails is clicked then that counts as one Product View.
If the user performs any other navigation action, e.g. clicks on a category, then the link to the ad is "broken" and subsequent product views no longer count as belonging to the Ads channel (they belong to the "Search Store" channel instead).
Sometimes a single view of a product is counted in multiple channels. For example, suppose the user was viewing a category, and they also entered text in the search box. In that case, the products that are shown as the results of the search will be counted in two channels: in the "Categories" channel, and in the "Keywords" channel.