SSDs are Solid State Drives, used for storage.
We offer four SSD sizes - all of the same NVME speed (up to 3,500 MB/s). Once you factor out speed, the choice is quite simple, similarly to RAM - the more complex tasks you are planning to perform, the more SSD memory you will need.
We recommend checking how much memory you have left on your current machine to estimate the needs of your future one.