For a security to be traded on an exchange, the issuer undergoes an admission procedure: confirming compliance with information disclosure requirements, issuance volume, existence period, and corporate governance standards. Securities that pass the procedure are included in a list divided into levels with varying strictness of requirements.
The listing level is an indirect guide for investors. A higher level implies greater volume of disclosed information and stricter conditions for the composition of governing bodies, which reduces information risk. It does not characterize the issuer's financial condition and does not guarantee returns.
The reverse procedure is delisting, removal of a security from the list. It occurs when requirements are not met, at the issuer's own decision, or during reorganization. For the owner, this means loss of exchange liquidity: the security remains their property, but it can only be sold on the over-the-counter market, usually at a worse price.
Practical conclusion: the mere fact of listing only means admission to trading, not that actual transactions occur in the security. Liquidity should be checked separately through trading history.