Since iOS 8, Apple's Quick Response feature has been able to respond to messages without leaving the lock screen or the current app. However, you can not use all message features if you respond in this way. You can not add photos, use iMessage apps, record audio, select effects, or send handwritten messages. You could not use Tapback either, but iOS 12 just changed that.
With Tapback, introduced in iOS 10, you can quickly respond to a message by using a small selection of expressions: a heart, thumbs up or down, haha, question mark and exclamation point. These effects only work for iMessages, but they can still be used for SMS texts that are translated into text (loved, liked, not liked, laughed at, highlighted, and interviewed).
To send a tapback icon in the News app, in a conversation thread, just double-tap the message you want to add the response to, and then tap the Tapback option. In iOS 1
When you receive a text message on your lock screen, press it with 3D Touch (or just tap an iPhone) SE or 5S) to quickly reply. This also works on the notification screen. When you receive a message in a banner on the home screen or in an app, swipe it to quickly reply. Just tap the message you want to add a tapback response to by tapping the message twice.
While iOS 10 and iOS 11 do not tapback in quick answers, they should probably have. Finally, tapback is there to send quick responses to your friends and family without you having to type. So it only makes sense that this function is available in quick answers. Why the two were not put together before is a question for another day.