Tooltip functionality has become the part of the web world where just on hover you get the more detail but not need to add their permanently.
Dynamics CRM does not support tooltip for the records. Simply you need to install the solution and configure it for the entity (for which you need to use) and you can see the tooltip for the records. Let's say, you are at contact record and you want to see details of account associate without actually jumping the page. You just need to hover on account field record and it will show the results.