A SPAC is a publicly listed shell with no operating business. It raises capital from public investors, then has a defined window (typically 18 to 24 months) to identify and merge with a private operating company. The merger ('de-SPAC') takes the operating company public without the traditional IPO process.
SPACs were extremely active in 2020 to 2021 but have since cooled significantly as many de-SPAC companies traded poorly and the SEC tightened scrutiny on forward-looking financials in SPAC mergers.