Like an external USB hard drive -- like this (below). Rather than an internal hard drive like you find in a PC tower.

https://www.bestbuy.com/site/wd-my-passport-1tb-external-usb-3-0-portable-hard-drive-blue/5605506.p?skuId=5605506&cmp=RMX&extStoreId=27&ref=212&loc=1&ksid=ce6081f9-7b0b-44f3-8340-ed06bcb3cb24&ksprof_id=8&ksaffcode=pg199138&ksdevice=c&lsft=ref:212,loc:2