HDDs or Hard Disk Drives are generally what you will find in most computers. SSDs are becoming quite common as of late. So which should you pick SSD VS HDD that is the question!
HDDs have spinning disks inside of them. Kind of like an old record player, or your CD/DVD player. The disks spin and like a record player an arm with the reader comes out and scans the disk for the information that it needs. HDDs are usually a good option if you just need a computer for general tasks, or not very demanding games. The other great thing about HDDs is since they have been around for a while the price to storage ratio is a lot cheaper than SSDs. So many people use HDDs and their large storage for back up Hard Drives or to store their game collection, movies music etc.
SSDs generally are smaller when it comes to storage size, are more expencive since they are a newer product. It has no moving parts inside of it. To put it bluntly it is basically just like the usb flash drive you may have used. It is connected inside the computer instead of through USB just like a HDD tho. So it has smaller storage size and more expensive. Why would you choose tho buy it then? That allows it to run faster than if it was connected by USB. So since it is a newer technology, you end up with a trade off.
HDD are generally cheaper and larger storage space inside of them. But not as fast as an SSD.
SSD are generally faster but are more expensive and smaller storage space.
Many people use a smaller SSD for their boot drive, so their computer turns on a lot faster and can perform tasks faster. But use a HDD for as stated above storing media and large files. It all depends on what you need, if you just plan to browse the web, play facebook games, and maybe watch youtube. Then an HDD should be more than fine for you. Save the money you would have spent on one, and spend it elsewhere in your build.
Unlike you CPU and Motherboard, if you change your mind later or want a bigger drive, or a faster one. It can be switched out later, but you will either need to reformat your pc, clone it, or use another method. But it is a lot easier to swap than those two previous parts.