投资 (tóuzī) is the standard term for investing money, both as a verb ('to invest') and a noun ('an investment'). 投入 (tóurù) also covers financial investment but is broader—it can also mean 'to put in' time or effort and describes being engrossed (e.g., 投入工作 'devoted to work'). 出资 (chūzī) is more formal and emphasizes providing capital, often in business partnerships.