The internal auditing will be in charge of the different issues that may be related to the various practices that are being done by the company plus all of the risks that the company has taken. External auditing will be more focused on the different financial records that people may have, plus all of the financial statements that were released by the company.
There is a lot of internal auditing that is done throughout the year, while external auditing would only need to be done once a year. Internal auditing is normally done in order to see if the operational activities of the firm are working properly or not. External auditing is focused on financial statements.