what is the use of @keyframes in css code example

Example 1: @keyframes

p {
  animation-duration: 25s;
  animation-name: slidein;
}

@keyframes slidein {
  from {
    margin-left: 100%;
    width: 300%;
  }
  75% {
    font-size: 300%;
    margin-left: 25%;
    width: 150%;
  }

  to {
    margin-left: 0%;
    width: 100%;
  }
}

Example 2: css key frame

div {
  width: 100px;
  height: 100px;
  background: red;
  position: relative;
  animation: mymove 5s infinite;
}

@keyframes mymove {
  0% {top: 0px;}
  50% {top: 50px;}
  75% {top: 40px;}
  100%{top: 0px;}
}

Example 3: css keyframes

@keyframes mymove {
  from {top: 0px;}
  to {top: 200px;}
}