Check out example codes for "unity rich text options". It will help you in understanding the concepts better.

Code Example 1

<!-- These are the richtext options unity supports -->

<b>bold</b> <!-- Renders the text in boldface. -->
<i>italics</i> <!-- Renders the text in italics. -->
<size=50>size</size> <!-- Sets the size of the text. -->
<color=#ff0000ff>color</color> <!-- Sets the color of the text. -->
<material=2>material</material> <!-- Sets the material of the text. -->
<quad material=1 size=20 x=0.1 y=0.1 width=0.5 height=0.5>
<!-- This is only useful for text meshes and renders an image 
inline with the text. -->

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