Normal Hard Drive (HDD/Hard Disk Drive) vs Solid State Drive (SSD).
Most Modern Laptops use SSD's. An SSD is basically a hard drive with no physical spinning disk and moving arm which reads the disk, which is what makes it so fast. Think of an SSD like a giant SD Card. On the other hand, an HDD has a spinning disk inside of it with a moving arm reading the disk, is more sensitive to movement, can be damaged if turned upsidedown or even slightly sideways, and can be damaged from rough movement. HDD's are slower because the moving hand inside of the structure constantly moving on the spinning disk to read data and transmit it to a computer. SSD's simply send data to a computer instantly instead of needing to read a spinning disk with a moving arm. SSD's also have a longer lifespan. 90% of HDD's have a lifespan of about 3.5 years, and 80% have a lifespan of 4.5 years. Almost every SSD has a lifespan of at least 7.5 years, while most have a lifespan of about 10 years.
Which should you get?:
Definitely an SSD. If you have a very low budget that can only purchase a device with an HDD or just an HDD, remember to back up your data to somewhere like Microsoft OneDrive often, as your HDD Can fail by simply dropping your device, shaking it, tilting it sideways or putting it upsidedown, or exposing the actual HDD disk to the outside air. If you drop an SSD, it will most likely not cause any damage. If you shake, tilt sideways or upsidedown, or expose an SSD to air, it will not fail.