A friend says his hard drive is broken?

Assuming the drive inside the external enclosure is mechanical. There is a read/write head moving really fast seeking for data on platters (like cds  but  metal), When the drive drops, the head can hit the platters, scratching them. Once the platters are scratched, the data can sometimes be read by professionals but they have to take the drive apart. This all has to be done in a clean room environment as dust can corrupt the data even more. Another thing that can happen is the head can stick to the drives so they can't spin...A controller board can also fry. 

Yes it can, the structure is damaged, making it unusable.

A "hard drive" is a type of storage device. More specifically, it is a DASD -- Direct Access Storage Device.  It records data on spinning disks. Read/write heads move across the surfaces of the disks to record and retrieve data. 

The distance between a read/write head may be a few microns -- much smaller than the diameter of a human hair. A running hard drive is delicate. If it is bumped, dropped or jarred, the head could come in contact with the platter. This is called a "head slap". If that happens, the head and platter will be damaged. The drive may work, but particles from the damage will shorten the life if the drive. This type of failure is also called a "head crash."

So, yes: It is possible for a running drive to be damaged by falling off a table. If the drive was not running, it could be damaged, but that is less likely. It also depends on the type of surface it lands on. Another factor is orientation: If it lands with the platters parallel to the floor, it is more likely to be damaged than if it lands on its side.

It may be possible to recover the data. But, it would be expensive.  If the platters (disks) and heads are not damaged, but some other component was damaged, it is possible for a data recovery service to remove the disk head assembly (the platters and heads as a unit) and place it into a specialized drive to recover the data. If the heads and/or the platter surfaces are damaged, they may be able to scan undamaged areas and recover some of the data. The data they can recover might include your files.

Comment:  An alternative to a hard drive that is becoming more popular is the SSD -- Sold-State Drive. These use electronic memory chips to hold data. 

Comment: Linus Tech Tips visits a company that makes data recovery tools https://www.youtube.com/watch?v=eyr14_B230o 

"beyond repair" could mean anything. it could mean that HE cannot figure out how to repair it.

you should tell him to give you the drive and you will fix it.

that said, hard drives are very volatile things, and should be treated like eggs when moving, even in a laptop. laptops were never meant to be moved while in use. dropping one from a table or countertop would cause about as much damage as dropping a DVD player with a DVD running in it. pretty bad for the baby.

The hard disc (also called a hard drive) is a precision electro-mechanical device where data is stored. The main one we use is inside the computer so it cannot fall on the floor unless removed. We may use an external hard drive for back-ups or 'overflow' storage or maybe for stuff we want to keep separate. It can stand light knocks, maybe even a fall to the floor, but there is no guarantee it will survive it. The revolving discs where data is stored are unlikely to come off their bearings but the read/write heads can be dislodged by a hard knock. If the read/write heads are not working, you can no longer get the data off the disc surface. It is POSSIBLE that a fall could cause the read/write heads to touch the disc surface, which can damage it.

Data can still be extracted from the hard disc by specialist labs but it is an expensive process so it is only worth it if the data is valuable and there is no back-up. There should ALWAYS be a back -up copy of important data.

Newer types of hard drive (SSDs) use blocks of memory chips with no moving parts so they are less easily damaged by knocks.

I have dropped hard disks without causing any damage. Maybe I was just lucky.