To place portlets vertically.
To place portlets horizontally.
If the web site uses CSS-columns horizontal layouts behave differently compared to when the site uses a layout based on tables. You then have to set a width on the content of the horizontal layout to make the content place horizontally.
The linked layout is utilized to reuse an already existing layout. You will then receive a copy of a whole layout with several portlets. It is also possible to use the linked layout when building templates compared to the Linked portlet which only displays content on the web site.
To find the “original layout" you right click on the linked portlet and choose Properties. There you find the alternative Source where the address to the page with the layout is located.
Adding layouts requires the right "Create layout".
Adding linked layouts requires the right "Create linked layout".