Check out example codes for "css grid example". It will help you in understanding the concepts better.

Code Example 1

<!-- HTML code -->
<div class="wrapper">
  <div class="box">A</div><div class="box">B</div><div class="box">C</div>
  <div class="box">D</div><div class="box">E</div><div class="box">F</div>
</div>

<!-- Css code -->
<style>
.wrapper {
  display: grid;
  grid-template-columns: 100px 100px 100px;
  grid-gap: 10px;
  background-color: #fff;
  color: #444;
}
.box {
  background-color: #444;
  color: #fff;
  border-radius: 5px;
  padding: 20px;
  font-size: 150%;
}
</style>

Code Example 2

.item-a {
  grid-area: header;
}
.item-b {
  grid-area: main;
}
.item-c {
  grid-area: sidebar;
}
.item-d {
  grid-area: footer;
}

.container {
  display: grid;
  grid-template-columns: 50px 50px 50px 50px;
  grid-template-rows: auto;
  grid-template-areas: 
    "header header header header"
    "main main . sidebar"
    "footer footer footer footer";
}

Code Example 3

.container {
  display: grid | inline-grid;
}

Code Example 4

grid-row-start:    2;
grid-row-end:      3;
grid-column-start: 2;
grid-column-end:   3;

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