Here I will show a simple way to make a toggle using only HTML5 and CSS3 files. It's beginner friendly, so there are a bunch of explanations. Chances are if you just see the code snippets you will understand. Let's go...

1. Add the HTML

<div class="toggle">
   <div class="toggle__cell"></div>
</div> 

2. Add the toggle event

To do so we are using an inline script right away in the toggle__cell element.

<div class="toggle">
   <div class="toggle__cell" onclick='this.classList.toggle("toggle--active")'></div>
</div> 

The this refers to the toggle__cell and whenever occur a click on it, a specific class to differ the non-toggled and toggled is added. Now let's jump into the CSS.

3. Windup with the CSS

Actually it is already working, the element now 'know' when it's toggled. Though, there's no visual signal for it, and with CSS we are making it done.

First, the style of toggle is the following

 .toggle {
            width: 50px;
            height: 23px;
            display: flex;
            align-items: center;
            background: #ffffff;
            box-shadow: inset 0 0 10px #e4e4e4;
            border-radius: 20px;
         }

We are putting the toggle__cell in the center using flex-box and adding a slight effect of shadow.

.toggle__cell {
            width: 15px;
            height: 15px;
            cursor: pointer;
            background: radial-gradient(#2d8ef5 30%, #a889fff1);
            border-radius: 50%;
            transition: transform ease-in-out 0.4s;
            transform: translateX(5px);
         }

Here we just make the cell combine with its father, a slight gradient, circle form and an initial placement with translateX to not touch the border-left of the father, but it could be made by tons of others approaches, such as padding or left positioning. Moreover there's the transition to turn the toggle sorta "pleasant", as well as adding the mouse cursor as it was a button.

Finally we make the visual difference between non-toggled and toggled:

.toggle--active {
            transform: translateX(30px);
         }