There are bound to have been discussions about this topic already.
There have also been discussions
about abstract classes,
and about how abstract classes differ from interfaces on these bulletin boards in the last couple of days.
Yes, you can get all the members of your superclass
via the subclass, provided you haven't given them private access, but
not vice versa.
the reason for using inheritance is that you will have lots of objects with commonc characteristics, for example if you have a Person class, you will have fields like name, dateOfBirth, address, etc.
You might extend your Person class to have an Adult class, with additional information eg National Insurance number (in UK) or Social Security number (in USA). Children don't have those data.
You can extend your Adult class to a Convict class with fields like offence, lengthOfSentence and prisonNumber. There are lots of Adults who don't have that information at all.
Now, what happens if there is a change in format of one of those data; those of us who are older can remember that postal codes were introduced in UK in the 1970s, and more recently the US zip code has changed from 5 digits to 9 digits. Or you want to add mobile number as well as phone number?
What you do is to go to the superclass, and change the fields and methods there; if it is done correctly, you can be confident that it will work for all the subclasses as well.
So using inheritance makes it much easier to have several similar classes which share common characteristics, and also to change them.
QED
CR