Do notebooks still have a hard drive?
Some do, others use a semiconductor drive or both.
Yes? Do you think the system etc. Is in the cloud?
Does a stick have a hard drive?
Some yes, but most of them now have an SSD and possibly an additional HDD for larger amounts of data.
There are also terrasticks, maybe notebooks also have a stick
Every storage medium has a storage unit, including a USB stick.
Storage unit and hard disk have a difference
Every storage medium is a hard drive somewhere…
The trend is clearly towards SSDs (which I personally still call hard drives, even if that is not entirely correct) or a combination of SSD and HDD.
Netbooks or tablets only have memory