<button type="submit" class='edit'>
<img src='https://via.placeholder.com/20x20' height='20px' width='20px'alt="edit">
<span class='tooltiptext'>Edit</span>
</button>

.edit {
  -webkit-appearance: none;
  -moz--appearance: none;
  appearance: none;
  display: block;
  position: relative;
  width: 20px;
  height: 20px;
  border: none;
  margin:0;
  padding: 0;
  border-radius: 0;
  background: none;
  cursor:pointer;
}

.tooltiptext {
  position: absolute;
  top: 100%;
  left: -999em;
  margin:2px;
  opacity: 0;
  width: 70px;
  background-color: #fff8dc;
  border: 1px solid #cbcbcb;
  border-radius: 6px;
  text-align: center;
  box-shadow:0 0 5px rgba(0,0,0,0.3);
  z-index: -1;
  transition: left 0s, opacity 0.5s ease;
}
.edit:hover .tooltiptext {
  left: 0;
  opacity: 1;
  z-index: 2;
}