The textbook wrote like the following:
A natural generalization is to consider a counting process for which the interarrival times are independent and identically distributed with an arbitrary distribution. Such a counting process is called a renewal process.
I understand from the above sentences that Renewal Process is a subset(specific type) of Counting Process.

However, the textbook wrote the definition like the following:
Definition 3.1.1
The counting process $\{N(t), t\ge0\}$ is called a renewal process.
I understand from the definition 3.1.1 the Counting Process is equal to the Renewal Process.
I want to know the relationship of the counting and renewal process.
Which one is subset of the other? Or Equal?
Thank you for reading my question.