Inventory consisting of impressions sold ahead of time rather than in a real-time auction via real-time bidding. Called guaranteed because the publisher signs a contract with an agency committing to deliver the specified impressions in exchange for an agreed-upon sum. If the guarantee is not met the agency will often request a “make-good ” usually in the form of a credit. See also premium inventory.

Gross Rating Point; the standard currency that broadcast TV has used to plan purchase and measure advertising campaigns since the 1950s. Defined as [reach x frequency] for a target demographic.

Geofencing is a location-based digital marketing tool that lets marketers send messages to smartphone users in a defined geographic area.  For example shoppers that arrive at a mall can be targeted with ads  by stores located in that mall simply because of their geographic location.  Digital marketers can take the gps capabilities to feed ads to people who are geographically ready to make sales decisions.

What is the GDPR?
The GDPR, or the General Data Protection Regulation, is a European privacy law approved by the European Commission in April 2016. The GDPR regulates, amongst other things, how organizations may obtain, use, and store the personal data of EU residents (the EU is comprised of 28 countries and 510M people).

At its core, the GDPR follows two main principles:

1. Consumers own their data
The GDPR enables EU citizens, not online vendors, to have the final say on how their data will be used. Thus, consumer consent is required for PII collection, sharing, and usage. The GDPR also introduces the idea of "data rights", whereby individuals have the right to see, edit, and delete data a 3rd-party has on them.

2. Companies need to protect this data
The GDPR imposes tighter restrictions on how companies handle PII. This includes limiting what they collect, adding better security protocols, hiring Data Protection Officers, having data breach notification plans, and more.

The first point will greatly impact the ad tech industry, as much of advertising relies on programmatic behavioral targeting using customer data (such as retargeting, cookie matching, mobile ID targeting, frequency capping, etc). It's likely the GDPR will negatively impact, if not cripple, many common advertising practices.