Phoenix.View.render_many

You're seeing just the function render_many, go back to Phoenix.View module for more information.
Link to this function

render_many(collection, view, template, assigns \\ %{})

View Source

Renders a collection.

A collection is any enumerable of structs. This function returns the rendered collection in a list:

render_many users, UserView, "show.html"

is roughly equivalent to:

Enum.map(users, fn user ->
  render(UserView, "show.html", user: user)
end)

The underlying user is passed to the view and template as :user, which is inferred from the view name. The name of the key in assigns can be customized with the :as option:

render_many users, UserView, "show.html", as: :data

is roughly equivalent to:

Enum.map(users, fn user ->
  render(UserView, "show.html", data: user)
end)