Hi Josephine,
You have two options for Employee Self Service. Both options can be used over the internet.
1. Thin client application - Ideal if you are using project management, or if your employee wants to access from one computer, many times.
2. ESS on the web - No installation required, just use a web browser.
You can use either of these, or even both.
For eg: Your employees can use thin client application, within the office(this will be much faster). And web browser when they are at home.
Hope this helps.
Biju.