问题:

and how does it differ from the regular connection string?

回答1:

Connecting with the instant client is no different than with the full stack client - all connect string formats are the same. If you installed the instant client in a non-standard location on the filesystem or are having problems connecting to the database listener, be sure that your TNS_ADMIN environment points to the directory that contains your tnsnames.ora and sqlnet.ora files,

回答2:

Here is a comprehensive list of connection strings for Oracle (http://www.connectionstrings.com/oracle)

回答3:

The format is:

name/pass@//host:1521/instance

Standard Oracle connect strings typically look like

name/pass@tnsentry

Where tnsentry has been defined by one of several means such as a tnsnames.ora file. idstram's answer has an excellent pointer if you're looking for more details.