page / field group is a container for a single entity
page list / field group list is a container for multiple entities that are ordered like a list
yet, when using pega, configuring a view for a step, adding a field and defining its type as a "field group" I can easily store/configure multiple entities by clicking "open" -> here I can add as many entitites as I want, in different types.
In other words: not only field group (list) but also field group allows me to add as many additional fields/entities into the "container"
I suspect the issue is w/ how you are defining entity.
An entity - as it relates to a data model - describes a thing (or, an object), such as a vehicle or person.
Attributes are used to describe the composition of the entity. A vehicle entity could be described with the following attributes: year, make, and model. The person entity might be described with the attributes first name, last name, favorite color, etc.
In Pega, a page (or field group) is a synonym for entity. The thing that allows me to add as many additional fields/entities into the "container" are the fields (or, attributes).
you are correct - both are examples of an entity + attributes.
but, notice the difference in plurality.
w/ the first entity, I need service at (only) this address. That is a field group (entity) described as having a street, city, and state.
w/ the second entity, there are multiple service providers I can choose from - each of whom have an address. Each service provider's address is still a field group (entity) described as having a street, city, and state. However, because there are multiple service providers, that field group is a list of service providers.
You would only define the entity (Service Provider) once. Then, because you want to collect more than one service provider, you declare the entity to be a list.
entity + attributes define a data object. ServiceAddress and ServiceProviders are both data objects.
one is singular, one is plural.
p.s. the singular vs plural naming convention is standard practice. Helps you easily spot what you are dealing with.