When you create a database instance, you define a database parameter file.
You can use the system default for the parameter file and then adjust the values to fit your requirements.
You also have the option of using the parameter file from another database instance. If you want to do this, you can either use a copy of the parameter file from a database instance on the same computer or copy the parameter file from a complete data backup of another database instance.
Using a copy of the parameter file of an existing database instance is a particularly good idea if, for example, you are planning to later import the data from this database instance into the new one, such as in the case of a database copy or setting up a standby instance. This way you can ensure that the data can be imported without issue and that the instance with the database copy or the standby instance behaves exactly like the source database.
Even if you only wish to have the new database instance consume less resources, you can create it using a copy of the parameter file of the source database and then change values you want to change later.