An uplisting is an application, not an offering, but the two usually travel together because meeting the minimum bid price and shareholder-equity tests often requires a reverse-split and a capital raise. Once listed, the stock becomes marginable, options can be listed on it, and funds barred from otc-markets can buy it.
The announcement is frequently traded aggressively on small caps. The disappointment comes when the accompanying raise and split arrive, since both are dilutive or optically punishing.
Example: a stock at $0.35 must reach a $4.00 minimum bid. A 1-for-15 reverse-split takes it to $5.25, the company raises $22M to clear the equity test, and the uplisting completes six weeks later.
Related: otc-markets, listing-standards, reverse-split, delisting, pink-sheets