Edit in JSFiddle

<h2>flex Grow Değerleri 0 </h2>
<div class="flex-container">
<div class="item">0</div>
<div class="item">0</div>
<div class="item">0</div>
</div>

<h2>flex Grow Değerleri 1 </h2>
<div class="flex-container">
<div class="item grow1">1 <br>İçerik Olan Öğe</div>
<div class="item grow1">1</div>
<div class="item grow1">1</div>
</div>

<h2>flex Grow Değerleri 1 ve 2</h2>
<div class="flex-container">
<div class="item grow1">1</div>
<div class="item grow2">2</div>
<div class="item grow1">1</div>
</div>

<h2>flex: 1 0 0; </h2>
<div class="flex-container">
<div class="item col3">33% <br>İçerik Olan Öğe</div>
<div class="item col3">33%</div>
<div class="item col3">33%</div>
</div>

*{
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
*::before, *::after{
  box-sizing: border-box;
}

.flex-container{
display: flex;
padding: 15px;
border: 1px solid #e2e2e2;
flex-wrap: wrap;
margin: 10px 0;
font-family: sans-serif;
}
.item{
  text-align: center;
  padding: 15px 30px;
  font-size: 30px;
  margin: 5px;
  font-weight: 600;
  color: #fff;
  background-color: orange;
}
.grow1{
  flex-grow: 1;
  background-color: #2da192; 
  

}
.grow2{
  flex-grow: 2;
   background-color: #f11a56; 
}
.col3{

    flex: 1;
}