VTI is an ETF that is basically representative of the entire US market. It is somewhat like holding a little bit of everything in the US market.
If you have a bunch of cash sitting in a savings account, and instead want that cash tethered to the swings of equities market, VTI is a reasonable choice.
QYLD is even more exotic. It seeks to track the CBOE NASDAQ-100 BuyWrite Index. That index in turn seeks to track the performance of a theoretical portfolio of the 100 largest NASDAQ stocks on which covered calls are written with a certain formula. Covered calls are a type of options strategy.
I'm just another rando on the internet, but I would recommend neither VYM nor QYLD to people new to investing who aren't sure what to buy. VTI is a far more appropriate suggestion. As would be VT (like VTI but looking at all stock markets), BND (index fund for US investment grade bonds), and maybe BNDX (ex-US investment-grade bonds with currency hedges)
If you are planning to use margin, I dearly hope you don't use Robin Hood. You can get much cheaper margin loan from other brokerages like Interactive Brokers (less than half as much).
Having understood that, the effective yearly simple interest rate on my particular Robinhood margin (extra buying power) is only 5%/year so all I have to do is earn higher than a 6% return each year. This last year, my return rate was 14%, so that margin was worthwhile.
If new to investing and you aren't sure what to invest in, I suggest investing in: VTI, VYM, or QYLD depending on your risk tolerance. I'm invested in all three.