When you click on the Explore button in Google Slides, you will see suggested design layouts for your slide - click on a layout to apply it to the slide.
For example, the following basic title slide:
Could be formatted to the following automatically using Explore:
Click on the Explore button in the bottom-right corner of the screen
Choose the design you wish to use
You can also use Explore to search for information to add to your presentation:
Click in the Search box along the top of the Explore pane
Type the text you wish to look for and press Return
Use the Cloud Search tab to view presentations on Google Drive that contain the search text
Use the Web tab to find websites containing the search text
Use the Images tab to view images for the search text - you can position the mouse over and image and click on the + icon to add the image to your slide