hi aman,
apex:pageBlockTable represents a table formatted and styled to look like a related list table.
apex:panelGrid is placed into a corresponding cell in the first row until the number of columns is reached. At that point, the next component wraps to the next row and is placed in the first cell.
<apex:page>
<apex:panelGrid columns=”3″ id=”theGrid”>
<apex:outputText value=”First” id=”theFirst”/>
<apex:outputText value=”Second” id=”theSecond”/>
<apex:outputText value=”Third” id=”theThird”/>
<apex:outputText value=”Fourth” id=”theFourth”/>
</apex:panelGrid>
</apex:page>