Standard Individual Export Licence (SIEL). This is for the export of specific controlled goods to a specific customer. This licence is generally valid for two years and is used for permanent exports. If the goods are to be exported temporarily, a temporary version of the SIEL would be used but that would only be valid for a year and the goods must be returned before the expiry of the licence.
Open General Export Licence (OGEL). You would apply for one of these if you had to export specified controlled goods on a regular basis (ie more than a handful of times). They remove the need to apply for SIELs, but they can be revoked if abused!