The DataTable is an in-memory representation of a block of 
data. We can create our own tables in code using a DataSet 
and the types defined in the System.Data.OleDb or 
System.Data.SqlClient namespaces. The following are the 
core properties that are used while creating a DataTable. 

CaseSensitive:   Indicates whether string comparisons in 
the table are case-sensitive or not.

ChildRelations:  Returns the collection of child relations 
of the DataTable (if any).

Columns:   Returns the collection of columns that belong to 
this table.

Constraints: Gets the constraints maintained by this table.

DataSet: Gets the dataset that contains this table.

DefaultView: Gets a customized view of the table that may 
include a filtered view or a cursor position.

MinimumCapacity: Gets/Sets the initial number of rows in 
the table.

ParentRelations: Gets the collection of parent relations 
for this table.

PrimaryKey: Gets/Sets a primary key for the table.

Rows: Returns the collection of rows that belong to this 
table.

TableName: Gets/Sets the name of the table.

Datatable is a sql class which is used to create a temporary
table and working on it at run time.

In ADO.NET, DataTable objects are used to represent the 
tables in a DataSet.
A DataTable represents one table of in-memory relational 
data; the data is local to the .NET-based application in 
which it resides.
A DataTable is a collection of DataRow and DataColumn 
objects.
The schema, or structure of a table is represented by 
columns and constraints.
You define the schema of a DataTable using DataColumn 
objects as well as ForeignKeyConstraint and 
UniqueConstraint objects.