This a utility/developer-only module for converting fields from one type to another. E.g., for changing plain text (textarea) fields to filtered text (WYSIWYG), or short text fields to long text. Existing field data is preserved as long as the new field type schema has columns with the same names as the old schema (e.g., "value").
This module provides a field widget and formatter to allow plain-text fields to act like filtered text fields. I.e., to change your textareas into WYSIWYGs without changing the underlying field type.