Configure connection string to SQL Server Express to work with every computer/server name

How do I have to configure my SQL Server Express connection string that the server attribute accepts the computername where the SQL Server is running aka the current machine:

<connectionStrings>
    <add name="MyDbConn1" 
         connectionString="Server=.\SQLEXPRESS;Database=MyDb;Trusted_Connection=Yes;"/>       
</connectionStrings>

I have seen somewhere a configuration like the above where the server attribute has the .\SQLEXPRESS value.

What does that dot notation mean?

via Chebli Mohamed