Columns in SharePoint apps are used to store data, and you need to define the type of column as you create it. By defining the type of column, you gain extra functionality based on that type, and you help to control the type of information that can be entered into the column and how that information is presented onscreen.
For example, users can enter only a number in a Number column; they can’t add miscellaneous text.
SharePoint provides a number of built-in column types that you can select for your apps, such as columns that know how to handle dates and URLs. Third-party companies and developers in your organization can also create custom column types that can be added to SharePoint.
For example, if your company needs a column that handles a full zip code (the zip code plus four numbers), a developer could create it for you.
Publishing HTML (an even richer form of text), can be selected when creating site columns in publishing sites for a large organization and need to have granular control on who can publish to which portions of a page.
When you’re creating columns for your custom app, you can change the order of the columns as they’re shown in the Columns section of the List Settings page. Changing the column ordering in this section helps with organizing the app flow for owners and how they display on the app’s form.
However, changing the order on the List Settings page doesn’t change the order of columns in the default view — you must modify the view separately.
Don’t underestimate descriptions! Creators of lists often carry a lot of information in their heads about the content in the app. Users aren’t mind readers. Make sure to type descriptions to help them understand the intent of the column and the data expected.