Junior SSD
A first website, a portfolio, a company presentation with a contact form. Ten gigabytes is a lot of space for a site that is mostly text and photographs, and the resource limits cover a steady stream of visitors without trouble.
Outgrow it when pages start queueing at busy hours, or when the mailbox fills the account.
Medior SSD
A business website that people actually visit, a small shop, or a few projects kept side by side. Twice the memory and twice the entry processes of the smaller plan, which is what matters when several visitors arrive at the same second.
This is the plan most customers stay on for years.
Senior SSD
Agencies and companies that keep a group of client sites in one account, with separate mailboxes and separate databases for each. Twenty one websites, forty gigabytes and four cores worth of processor time.
If one of those sites needs its own machine, tell us and we will say so.