Reaching people who may not have been to your website yet but might be interested in your ad and one way to do this is within audience targeting. In market audience targeting is a setting that allows you to serve an ad to somebody who has exhibited a particular behaviour or set of behaviour that signal there in market.So according to the Google to qualify someone as being in market for a specific product or service Google takes into account clicks on related add subsequent conversions along with the content of the sites and pages people are visiting.

The recency and frequency of those in-market audiences are people who are temporary interested with the topic which are made available for you to target. If somebody is in market for a particular product or service they are going to be more receptive to relevant ads which is win for the users and for advertisers. 

This is another feature of AdWords platform designed to help get the right people to see your ads at the right time while filtering out people who are going to be less likely to be interested.

Two things to keep in mind with in – market audiences among them the first one is that people are constantly entering into and exiting out of audiences so new users will be joining and old users will be living based on that behaviour.The second thing is the additional targeting later layers can and I think definitely should be applied.