CS2 Prime status is the paid tier of a free-to-play game. Counter-Strike 2 can be installed and played for free, but the free version has limits. Prime removes them. It is a single purchase of the Prime Status Upgrade, not a subscription, and it stays on the account.
For traders, the important part is drops. Only Prime accounts receive the weekly care package with cases, skins and graffiti. A free account can still trade, buy and sell items and open cases, but it never receives free items from playing. Valve set this rule in its Adjustments to Non-Prime post of June 2021: non-Prime accounts no longer receive XP, Ranks, drops or Skill Groups.
What does Prime status include?
According to that same Valve post, Prime accounts get XP, ranks and skill groups, item drops, and access to ranked matches, which are always played only with other Prime players. Non-Prime accounts are limited to unranked matches.
Prime used to be earnable by reaching a certain in-game level, and accounts that earned it that way keep it. Since the June 2021 change there is no longer a free path to Prime, so new accounts can only get it by buying the upgrade.
Is Prime status worth it for drops alone?
It depends on how much you play. If you earn drops most weeks, the cases can add up over a year, especially if you hold cases that later leave the drop pool. If you play rarely, the drops will not cover the price. The matchmaking benefits are the main reason most players buy it.
Prime is tied to the Steam account and cannot be moved or sold. Anyone offering to sell you a Prime account is offering an account transfer, which the Steam Subscriber Agreement does not allow, and it is a common route to losing both the money and the account.