In SharePoint 2013, What are the differences between Standard vs Enterprise Search?
And does it comes with different licensing when purchasing the SharePoint 2013 Enterprise version?
Check out the following comparison chart:
It boils down to this:
The advanced search stuff not many companies use - the Content Search WebPart is interesting though. Licensing is done through CALs (Client Access License) per User. That means you would need a Standard/Enterprise license per user who uses Enterprise features. If you're talking about search, it might very well be all your users. There is a price difference between the Standard and the Enterprise CAL.