Although most use the term eSIM, it is more technically correct to say Embedded Universal Integrated Circuit Card (eUICC). This refers to a particular type of SIM software that enables a physical SIM, could be card format of embedded chip format, to host multiple profiles. eUICC also makes it possible to add, remove, and manage these profiles via a method known as Remote SIM Provisioning (RSP).
When it is first switched on, a device with an eUICC SIM needs a way of making communication with the network server that controls the subscription on that device. A bootstrap profile provides the credentials for this initial default connection.
In other words, the bootstrap profile is loaded onto the eSIM during the SIM manufacturing stage and when activated and deployed in an IoT device, enables access to the service providers mobile network and to roaming network partners as defined by the profile.
The bootstrap can serve as a long term operational profile if appropriate or it can be replaced if required. New operational profiles are usually downloaded in order to switch network providers or tariffs to local country or regional options, to economise on costs or to resolve performance or quality issues should they arise in the future.
Downloading or switching profiles happens under the control of an RSP system which will conduct profile update ‘campaigns’ which can be setup via APIs or automated via a rules engine.