Sub Domains

Sub domains will be manageable at hosting control panel:

You may create new sub domains, remove existing ones or redirect them to another site/page.

Once you created a sub domain like sub1.my_domain.com a folder with the same name as the sub domain (in this example "sub1") will create under the public_html folder of your account, That will be the home folder of that sub domain, Any one who attempt to see your subdomain using a browser will see the contents of that folder, So you may for instance put some web files and start with an index.htm and make it a completely separated web site.

You may also check the usage statistics of each subdomain separately from top domain at hosting control panel:

Once a subdomain created a similar account will create in the FTP accounts list, For example if you create sub1.my_domain.com ftp account will be sub1@my_domain.com, you may use it to login to your account and it will go directly to the home folder of that subdomain. Make sure to login with full email address form of created FTP account or it will not work.