アメリカと日本の違うところ：チップの理由 第二 U.S. and Japan Differences: The Reason for Tipping, Part 2 インクル英会話掛川市
Read tipping part 1 here.
The idea behind tipping is that good service (like a waiter refilling your drink promptly or being very friendly) should be rewarded. If you liked the service you received, you can give the waiter a generous tip to show your appreciation. This is usually 20% or more of the bill at a restaurant, which is higher than the regular 15% that people give. Also, customers and managers may view tipping as a way to motivate employees like waiters to provide better service or be nicer to customers.
-to reward 報いる
-to receive もらう