You can create and assign portfolio categories in the sidebar of edit/add portfolio page as shown below –
https://docs.google.com/file/d/0B9j6FQo4cSQFM3ZPVzB6TUp0V2s/edit?usp=drivesdk
These categories are sufficient to pull them into separate pages using the shortcodes I linked to earlier. The slug is used to create a URL for a category and you can see the slugs as shown below –
https://docs.google.com/file/d/0B9j6FQo4cSQFM3ZPVzB6TUp0V2s/edit?usp=drivesdk
Looks like you are really new to WordPress. I would urge to start with some introductory videos on WordPress in YouTube. There are plenty of them. Thanks