A warrant gives holders the right to purchase more shares at a set price on a later date. Warrants are given as additional compensation to pre-listing SPAC IPO* investors for agreeing to have their capital held in a trust until the merger.
*Not all SPAC IPOs come with warrants. To see if the SPAC IPO you are wanting to purchase comes with warrants, you will want to review the information provided about that specific SPAC IPO.