A SSD and a HDD are both types of Hard Drives. An SSD is a newer, more advanced Hard Drive that doesn’t include moving parts. The standard Hard Drive was first introduced by IBM in 1956 which is a long time. An SSD lasts longer then the standard Hard Drive making it more expensive then a HDD. The form factor is the same and most new computers come with a SSD.
A SSD allows quicker boot up times and quicker access to other data on the Hard Drive since it stores data on microchips. Since a Solid State Drive doesn’t have any moving parts it also has a better chance of not breaking if dropped accidentally. If you are looking to replace or update your hard drive an SSD is the better choice. The only real benefit of a standard Hard Drive is the price making it the cheaper option.