Visualforce page to display global variable

Use global variables in Visualforce page to access and display system values and resources in your Visualforce markup.

e.g. here the page provides information about the logged-in user in a global variable called $User.

You can access fields of the $User global variable using an expression like {! $GlobalName.fieldName }.

Example -

<apex:page>

    <apex:pageBlock title="Logged in User Status">

        <apex:pageBlockSection columns="1">

            {! $User.FirstName } {! $User.LastName }

           ({! $User.Username })

        </apex:pageBlockSection>

    </apex:pageBlock>

</apex:page>

Reference:

https://trailhead.salesforce.com/content/learn/modules/visualforce_fundamentals

https://developer.salesforce.com/docs/atlas.en-us.pages.meta/pages/pages_intro_what_is_it.htm

Visual:

https://www.youtube.com/watch?v=kDZa6CF1KF8