Note: answer amended with input from @goldilocks.
What your friend perhaps meant was to check the SD card for bad sectors.
A SD card, just like SSD, are subject to wear when cells are written. Depending on the card quality and how full the file system is, corruption of cells can happen rather quickly. On a SSD, the embedded microcontroller usually take care of managing this bad cells and has often many spare cells which it can use instead. On a SD card, there are no spare cells and the microcontroller in it does a much simpler job at managing bad cells and there are no interface to report back to the OS of this issue. So basically once a cell has become bad, you need to check your filesystems.
Trying to fix your SD card
Note: the Raspberry Pi has at least 2 partitions, a FAT32 (aka vfat) one where the kernel and releated data (aka firmware) are located. FAT32 can avoid bad sectors if instructed to do so, but I am not sure that the Linux tools support that for FAT32. However, it would be surprising that you have bad sectors on this partition as it is seldom written too.
You need to repair your filesystem and do some simple bad block checking. Run on the other partitions (with the exception of the 1st vfat one):
$ sudo fsck -vcf /dev/<device>
<device> by the partition, example:
As a last resort, you could use the badblocks utility (run
badblocks -nsv /dev/<device> on each partition of your SD card, obviously you need to do that from another Linux computer or from within a VM running on your desktop/laptop). This will tell you how many bad blocks are. If you have any bad blocks, you can let know your filesystem so that it avoids them. However there is a limitation, the badblock utility on SD cards will only work for allocated blocks, not the free ones (where you might still have bad blocks).
If the card is not repairable
If you have too many blocks broken, it is possible that you cannot use your SD card anymore as you might not be able to flash the image on the SD card without ending up with a corrupt file system. The solution is most likely to buy a new SD card, but this time not a cheap one :-) I've bought 2 safe brand for SD card, and one is running now for 1,5y and the other for 1y.