Display the status of an Ajax update request using actionStatus component

<apex:actionStatus> component:

A component that displays the status of an AJAX update request. An AJAX request can either be in progress or complete.
<apex:page standardController="Account">
<apex:form >
<apex:pageBlock mode="mainDetail">

<apex:actionStatus id="showStatus">
<apex:facet name="start">
<apex:image value="/img/loading.gif"/>
</apex:facet>
</apex:actionStatus>
<apex:pageBlockSection title="Account Information" id="redSection">
<apex:inputField value="{!Account.Name}" required="true" />
<apex:pageBlockSectionItem ><apex:outputLabel > Type</apex:outputLabel>
<apex:actionRegion >
<apex:inputField value="{!Account.Type}" >
<apex:actionSupport event="onchange" reRender="ajaxReq" status="showStatus" />
</apex:inputField>
</apex:actionRegion>
</apex:pageBlockSectionItem>
</apex:pageBlockSection>
<apex:outputPanel id="ajaxReq">
<apex:pageBlockSection title="Account Description" id="greenSection">
<apex:inputField value="{!Account.Description}" rendered="{!IF(Account.Type == 'Other', true, false)}" />
</apex:pageBlockSection>
</apex:outputPanel>
<apex:pageBlockButtons >
<apex:commandButton value="Save" action="{!save}" />
</apex:pageBlockButtons>
</apex:pageBlock>
</apex:form>
</apex:page>
Explanation:

In the above example, <apex:actionStatus> component displays the status of an AJAX update request.

<apex:facet name=”start”> A placeholder for content that's rendered in a specific part of the parent component. Name=”start” is the name of the facet to be rendered.

<apex:image value="/img/loading.gif"/> is the syntax to display image. Here loading is image name of type .png.
Refer this Status attribute (In actionSupport )component in actionStatus component using id actionStatus component.

Output: Status will be displayed when a user selects "Type" picklist value

User-added image