An object defined primarily by its identity that can change over time.
An object with the purpose of store and retrieve entities. Its form should be indipendent from the data source.
A Service is an object that orchestrates the steps required to fulfill the commands imposed by the client. Notice that in DDD there are three different kind of services: Domain, Application and Infrastructure. However, this classification lose some of its importance for a fronte-end application.
Value Objects are objects that are known only by their properties and values. Adresses, 2D Points and other immutable structures are designable with Value Objects.
An Aggregate is a cluster of domain objects (entities or value objects) that can be treated as a single unit. Their main purpose is to ensure the validity of the business rules related to the domain.
Something happened that is relevant to the domain, their name should be in past tense, in order to communicate that something is already happened in the system.