It's an ETF, you can buy as much or as little as you want. My understanding is that they take their money and sell options (covered calls) with at-the-money strike prices on NASDAQ. Each month, they pay out dividends, something like 1% per month (bit over 12% on a yearly basis). So if you park 100$, you get like a free dollar per month, or 12 per year.

It's not hugely popular because you pay short term gains taxes on the dividends, a lot of tech does better than 12%, the shares can decrease in value if NASDAQ goes down, and if you wanted to (and had the startup cash), you could do the exact same thing without paying the ETF fees - buy 100 shares of QQQ for 62k, then sell a covered call for a month out, rinse repeat