Tweening is a term that's not used too often in CSS. It has its roots in computer animation and products like Flash. In tweening, rather than telling the program exactly how to render each frame, the animator/designer would tell the program what position the objects are in at two "keyframes" while the program figures out how to do the transition of the objects between the two mentioned points.

Here’s an example of sliding in an

element from the left side of a browser screen using tweening.

BY Best Interview Question ON 11 Mar 2020

Example

p {
animation-duration: 4s;
animation-name:tweening;
}
@keyframes slidein {
from {
margin-right: 100%;
width: 300%;
}
to {
margin-right: 0%;
width: 100%;
}
}