Controlled goods are items or products that require special permission from the government before they can be exported and are subject to a system of export licensing requirements.
Controlled goods can encompass a wide range of items, including military equipment, dual-use goods (goods with both civilian and military applications), certain chemicals, technology, software, etc.
Exporters must typically obtain the necessary permits before exporting controlled goods. Failure to comply with these regulations can result in legal consequences, including fines or penalties. UK Strategic Export Control Lists (SECList) define the specific controlled goods.
Read more about controlled goods here.