Court documents from Oracle's lawsuit against Google revealed that the search giant has paid Apple $1 billion in 2014 to be the preferred search engine on iPhones and iPads. While the terms of the agreement were not divulged in full, it was stated that Google was giving Apple a cut of the revenue generated from ads on the platform.

From Bloomberg:

Annette Hurst, the Oracle attorney who disclosed details of the Google-Apple agreement at last week's court hearing, said a Google witness questioned during pretrial information said that "at one point in time the revenue share was 34 percent." It wasn't clear from the transcript whether that percentage is the amount of revenue kept by Google or paid to Apple.

Google's lawyers requested to have the transcripts sealed, stating that the terms of its agreement with Apple are "highly sensitive:"

The specific financial terms of Google's agreement with Apple are highly sensitive to both Google and Apple. Both Apple and Google have always treated this information as extremely confidential.

Source: Bloomberg