Solution templates are pre-configured blueprints for virtual environments and services which allow for consistent and quick deployments. They ensure that each deployment adheres to certain standards and reduces the time and effort needed to set up complex environments. OS templates refer to pre-configured operating system images, and while they are a possible component of a solution template, they are not the overarching category. API gateways are components that allow for secure data transfer between systems but do not define deployment processes. Compute instances are the VMs themselves, with no relation to the templated deployment processes.