Somebody help me understand stocks

Start here.

What OceanMan said.

I'll add that one big reason for sticking with indexes is that most people can't pick stocks well to save their own life. Even professional investors generally have a hard time doing better than an index fund over time.

The key is "over time". Any given day a pro might be able to zig when the market zagged. But it goes the other way around too, hardly anyone is really able to do it consistently over a period of decades.

It might be different if you are an insider and really do know something nobody else does. For example, for a long time insider trading was perfectly legal if you were in Congress. They'd listen to testimony and run out and buy or sell as appropriate. Eventually someone found out they were making outsize returns and it was outlawed but it might have come back by now, not really sure.

But for you and me, sticking with an index is usually the way to go. Look for a "target retirement" fund - these are funds that will automatically pick a mix of stocks and bonds that is aggressive when you're young but gets more conservative as you get closer to retirement.

Lastly, read a bunch. Learn the difference between different kinds of accounts (IRA, 401, etc.). It isn't rocket science but you have to understand it in order to make choices that at least aren't terrible.

Dow at 24,000 is nothing but a number that gauges 30 large American companies (and these companies change from year to year)
It's a composite or an average of those companies that tracks the daily movement of them.

If the Dow opens at 24,000 in the morning and closes up 1% then it'll finish at 24,240, which is a pretty good day.

The S&P 500 is also an American index that tracks roughly the largest 500 companies in the country. From tech to telecommunications to utilities (many sectors).

The Nasdaq is yet another American index that tracks only technology companies.

You can buy the entire Dow index through many different avenues. Dozens of financial companies offer bundles of stocks call index funds that track the movement of the indexes that they represent.

For example, QQQ is an ETF (Exchange Traded Fund- A fund that you can buy and sell daily...as opposed to a mutual fund which can't be bought and sold as frequently)
QQQ represents the Nasdaq composite. You can buy it for around $150. It was around $120 this time last year. A financial company called Invesco created this fund.
Vanguard, another financial company, sells an ETF that does a similar thing under a different name, VGT.
Vanguard also sells VOO, which tracks the S&P500.
Spidershares DIA tracks the Dow30, and so on...

Buying one of these funds mentioned above on a consistent basis is called indexing.
You'll need to sign up at a brokerage account to start doing this. Investing 200 to $500 per month in index funds for 30 years has historically allowed people to be fairly comfortable in retirement. That's the goal.
If you contribute/invest $100,000 of YOUR money during a 30 year stretch then hopefully you'll have much more based on an average of 7% annual return.
You'll never be rich that way, but it is the recommended method for attaining financial security.

There are dozens of topics to discuss. From dividends, dividend reinvestment, individual stocks, bonds, allocation, diversification, options, 3x leveraged ETFs, short, long, day trades, swing trades, etc.

Everything I just mentioned I've learned here on Tigerdroppings. If you love learning and education in general get after it! If not, hire a financial advisor.

I’ve known several people who began contributing to a 401k around age 35 and retired comfortably at 63 or so.