Without going more back into history, I started with computers when Floppy Disks were the most effective way to transport information between computers. The Floppy was able to store up to 1.4 MB of information on each drive, then the ZIP drive arrived without too much success because it was expensive, but it was able to hold 100 MB in a single disk. It lasted enough to receive the CD at a much lower price per disc, holding 650 MB. Then till not so long ago, the DVD holding 4.7 to 9 GB of information was something very common to see, and you could frequently find a DVD recorder in almost any desktop or laptop computer.
Almost in parallel with the DVD the USB flash drive started to become something very common to see and very affordable, nowadays you can get a 64 GB flash drive for just USD 50. And you can store, delete and save again almost anything you want in it. The latest ones with USB 3 are very fast and it has been till now, the most preferred way to transport middle amount of data between places. Some people also use them as a backup media, although I don’t think is the best way to save things for backup on a USB flash drive, yes it better than nothing, but because it can get easily lost, so if you are using a flash drive to copy your stuff, make sure to keep it in a safe place. Also external hard drives which offer bigger amounts of storage for a friendlier price (1 TB for USD 70 aprox), are being used sometimes for backups, and to carry big amounts of information. Although some flash drives or pendrives (the bigger ones) will still be used for a while, the time of the smaller ones has come to a practical end.