You can create as many columns as you want, they will stack horizontally.
in column settings you can change the column name and/or background color. note: background color will choose a contrasting color for text (white for darker colors and black for lighter colors). In the project settings, you can enable auto color, so when a column is created, the background color is automatically generated for it (you can still change it if you don't like the color).
here you can set what sort of automation can be done to a card when a card is added to the column (either creating it new or moving it to it).
here you can restrict the column to an existing team member or select directly from the team. when you restrict a column, then that user/group will be the only one to create new cards or move cards to the column. other users will be able to comment on the cards, and project owners permissions remain unaffected by this option.
You can rearrange columns in any order you like, grab a hold of the column's title area and drag them left or right.
You can delete any column you want, but if it contains any cards, the cards will go into the project's archive section. so if you accidentally delete an important card, you can retrieve it from the archive at any time.