If your text could contain multiple lines of text, such as multiple paragraphs or other text that contains line breaks, you must use one of the long text field types.
Even if your text will not have line breaks, if it will be long enough that you want the expanded box for typing text, consider using a long text field instead of a single line text field.
If your text will be used in a computed field, such as a formula, lookup, or rollup, do not use rich text. The rich text formatting will not carry over in the computed field.
