If you go to "Setup > Edit Mapping", you will get a screen that's similar to the one below. On the left side, you have the "Import fields", which are the fields that Channable found in your import feed or import webshop connection. On the right side you have the "Internal Channable fields", where you can set the name for the Import fields as soon as they enter Channable.
By checking the "Custom" checkbox on the right side, you can freely name your field anything. However, if you uncheck the "Custom" checkbox, you will get a dropdown menu with the standard internal field names within Channable. The standard internal fields in Channable are the most common fields used in imports and exports, like 'price', 'stock' and 'brand'.
What is the difference between a standard field and a custom field in the import mapping?
The standard fields in Channable are the most common fields used in imports and exports, like the price or brand. Some of the standard fields have special properties. For example, the 'ean' and 'gtin' standard fields have an option to be validated in a rule, but are limited in applying other kinds of rules. The date fields also have specific date rule options.
Other than the special properties, there is no difference in custom or standard fields. Channable will automatically map your imported fields to standard internal fields if they match, but you are free to make it a custom field if you want to change the internal Channable field name.
When will the fields I mapped in my import be automatically mapped to fields in an export Feed or API?
Your internal fields, as mapped in your import mapping, will be automatically mapped to fields in an export channel (i.e. the Finalize step of a Feed, or the Build step of an API) when they are named the same. So, for example, your 'price' field is automatically mapped to the Price field of an API in the Build step. If the name doesn't match, for example if you have a field called 'stock_quantity' instead of 'stock', you will probably need to map this field to the Stock field in the Build step manually.