A section of data within an <apex:pageBlock> component, similar to a section in a standard Salesforce page layout definition.
An <apex:pageBlockSection> component consists of one or more columns, each of which spans two cells:
one for a field's label, and one for its value. Each component found in the body of an
<apex:pageBlockSection> is placed into the next cell in a 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.
To add a field from a Salesforce object to an <apex:pageBlockSection>, use an <apex:inputField> or
<apex:outputField> component. Each of these components automatically displays with the field's associated label. To add fields for variables or methods that are not based on Salesforce object fields, or to customize the format of Salesforce object field labels, use an <apex:pageBlockSectionItem> component.
Each <apex:inputField>, <apex:outputField>, or <apex:pageBlockSectionItem> component spans both cells of a single column.