The definitions of these categories are as follows:
Loan Service. Loan Service is defined as being the loan of Service personnel from the United Kingdom Armed Forces to assist a Commonwealth or foreign country. Loan Service personnel are subject to United Kingdom Service regulations; they are administered and receive pay and allowances in the usual way and are consequently subject to United Kingdom income tax. They are not subject to Host Nation taxation.
Exchange Officers. Exchange officers are deployed into key posts globally. They may be deployed for Service-specific or joint operational reasons. They work for the HN, usually in exchange for a HN officer working in the UK. They create Defence Engagement effect by projecting a positive image of the UK, generating understanding of host nation tactics, procedures and capability, and symbolising the close cooperative relationship between services. Exchange officers provide an opportunity to assist UK efforts in other ways, such as by gaining insight into another nation's ways of thinking or working practices.
Liaison Officers. Defence deploys a wide range of liaison officers to foreign militaries and sometimes elsewhere within a foreign partner's security architecture. Liaison officers are specifically intended to facilitate information sharing and provide a means to deliver persistent influence on the HN. In general, liaison officers remain under the command and control of the sending nation.
Embedded Officers. The UK also has a significant number of embedded officers, mainly serving in US headquarters. Embedded officers create tailored DE effect, depending on their role and the agreement of the HN. In general, embedded officers come under the command and control of the HN.
Secondee Service. Secondee Service places UK military personnel within a company, such as BAE Systems or NETMA. While such service is considered a tour of duty it is governed by bespoke TACOS for the duration of the secondment, agreed between the Company, the individual and the RAF. Seconded personnel temporarily leave the Air Force, are paid by the company but retain their right to promotion etc. Seconded service supports DE access and influence in a similar way to loan service.
 Embedded UK personnel operate as if they were the host nation's personnel under that nations' chain of command, but they remain subject to UK domestic, international and host nation law'.