Field Label and Machine Name explained
The Customer Account Fields app allows you to label each field for administrators. The label used is not shown to your customers, it is only for administrative use.
Each field's label is automatically turned into the field's machine name.
During field creation, you may edit a field's machine name by clicking on it. After creation, machine names are no longer editable.
Machine Names are used for identification in import and export files and throughout our systems.