• Yelp deals are promotions ran through Yelp.com that encourage new customers to visit your restaurant by offering them a discount on $X dollars at your place.
• Yelp gift certificates offer customers a discounted gift certificate to use on future visits.
• Yelp check-in offers incentivize customers to check-in to your place on Yelp and share the experience on Facebook and Twitter.
• Yelp search marketing allows your restaurant to appear as a "featured result" to customers who are searching for restaurants on Yelp. This allows your restaurant to leverage it's positive reviews and rank in front of your competition on search results.
• Yelp display advertising allows you to create and display banner ads on Yelp's website. This is typically used by national brands (not local restaurants).

All of these strategies help you create a better experiences for customers that are already likely to leave reviews as well as affordably acquire new customers.