This is the technical platform that enables the functions below.
A partner is a user on the platform that can use the functions below.
An installation is the envelope for a project, usually a Magento 2 production web-site.
An installation will have one or more deployments. A deployment is a running Magento 2 instance. The installation can have one production deployment (e.g. www.customer.com). It may also have several other deployments for development and testing (e.g. stage.customer.com, test1.customer.com).
A package contains the Magento 2 software and all the add-ons and modifications that the partner chooses to add. The package can then be used in one or more deployments. Packages have version numbers; any changes to a package will create a new version of it. This combination of a package and an associated version can then be used by a deployment. A deployment can easily be updated to a new package version, usually with less than a second of downtime.
A partner will have at least one database server. This is a SQL server that may host many deployments. When creating a new deployment, a database is selected. Different servers can be set up and each may be used for different task, for example a server for production sites, another one for tests, etc. Database servers have a fixed monthly cost regardless of usage.