Google Ad Grantees receive free AdWords advertising on Google search result pages.
This is the 'non-profit edition' of AdWords, which gives non-profit organisations such as your church a grant for free AdWords advertising on Google.com with a daily budget set to $329 USD.
If you're not familiar with AdWords, this is simply a Google tool that you can use to create ads, choosing keywords that are phrases or words related to your church.
When people search one of your keywords on Google.com then your ad may pop up next to the search results, advertising to an audience that is interested in your church.
This can in turn help you to attract members, so that people able to click on your ad to learn more about your church.