Can the H2 database be accessed via a terminal?

No, I think it is not possible.

http://www.h2database.com/html/main.html

Postgresql and Sqlite and others have that feature I think, but not H2 database.

H2 has a nice GUI feature.

Have you watched Chris 'Spring with Hibernate' video:

https://teamtreehouse.com/library/create-a-sessionfactory-and-datasource

In this video, Chris starts his database as a server database, so URL should be different.

But for testing purposes, and if you are beginner, it is better to fire up server base database.

So your hibernate.cfg.xml should be changed to

<hibernate-configuration>
    <session-factory>
        <!-- Database connection setting -->
        <property name="connection.driver_class">org.h2.Driver</property>

       <!-- server based database -->
        <property name="connection.url">jdbc:h2:tcp://localhost/./data/contactmgr</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.H2Dialect</property>

        <!-- Update the database schema on startup -->
        <property name="hbm2ddl.auto">update</property>

        <!-- Show the queries prepared by Hibernate -->
        <property name="show_sql">true</property>

        <!-- Names the annotated entity classes -->
        <mapping class="com.teamtreehouse.contactmgr.model.Contact" />
    </session-factory>
</hibernate-configuration>

You can also see GUI for embedded database by running java -jar h2*.jar, but it can be problematic with embedded databases because, embedded databases allow ONLY one connection, i.e. you cannot use database in your Java Application and simultaneously use GUI to see your database.

Anyway. All information is here:

http://www.h2database.com/html/cheatSheet.html

And please watch Chris video, disregard Spring details, just see how he fires up H2 database GUI console