Connection string is a string that specifies information about a data source and the means of connecting to it. It is passed in code to an underlying driver or provider in order to initiate the connection. Whilst commonly used for a database connection, the data source could also be a spreadsheet or text file.
The connection string may include attributes such as the name of the driver, server and database as well as security information such as user name and password
SqlConnection cn=new SqlConnection(“servername”;”database”;”uerid”;”password”);
//these lines are for creating a new connection by passing server name,uid,password and name of the database
SqlConnection con = new SqlConnection("server=abc-pc1\\sqlexpress; database=mind; uid=sa; password=sa ");