OpenStax has free, college level books available online, without registration (although if you register it will save sections you highlight for later review). In their business section, one called Principles of Finance seems to match what you’re wanting to learn. It’s structured more around learning business related finances than personal ones, but the underlying principles are much the same for both.

You’ve got equities, debt and derivatives.

Equities are ownership into shares. These are the simplest to understand. You own a share of a company and thus are entitled to a % of the profits (though most companies today choose 0% as their decision).

Debt means funding… debt. SLABs (student loan backed securities), MBS (mortgage backed securities), bonds (government debt), bank loans etc. etc. These are surprisingly complex in practice but perhaps easiest to understand. There’s lots of different details to debt (callable, puttable, tax free, convertible, coupons, notes, bills, bonds, I-bonds, EBonds, 10Y, 3M, overnight repos). But in all cases, you lend money to someone, and later they try to return it to you + a little extra.

Derivatives (usually options but there are many kinds) are new inventions that are more complex. Ignore these as they are very very complex.

That’s about it.

The general recommendation is to buy an ETF for equities and an ETF for Bonds. ETF is just a combination of simpler investments that you pay 0.04% to 2% a year for convenience.

VOO takes the 500 biggest companies in the USA (aka the S&P 500) and buys mostly the biggest company and a very little bit of #500.

BND is a similar idea except it’s a whole bunch of different debts from across the entire economy.

So buy some equities (mostly equities), some bonds, and leave some cash in a high yield savings account. Done.

Stocks (aka VOO) make the most money on the average, but also loses money the most often.

Bonds (aka BND) makes middle amount of money but rarely loses money.

Cash / savings accounts never lose money (except inflation). But makes very very little. It’s still worthwhile to keep necessarily amounts as cash and this you should always be considering how much cash to keep.

For personal finance you can’t go wrong with The Index Card which you can see here or read the book if you want greater detail

I learned a whole lot out of college from the “Choose FI” podcast. Listened to it while commuting to work. Go to their website and look up their recommended watch order and go from there. They have a lot of good ideas to get started.