Text Formatting ⇒ {0.49\textwidth} - What this command do?

[artemff]

{0.49\textwidth} I viewed it in my Latex book.

[frabjous]

It doesn't do anything on its own. It is a length--it means 0.49 times (or 49% of) the width of the part of the page containing text. So in a certain context, it might be used to tell LaTeX that something ought to take up a little less than half the width of the page. But we'd need to know what context it appears in to know precisely what it does.