This topic could literally fill a university library with prose, so this comment is just a tip of what to consider... I'm just going to try and give you pointers to search for on your own and things to consider which maybe a 23yo wouldn't normally consider. Oh, and don't feel bad if you can't afford or plan everything today, you're just at the start of a great and evolving journey.

At a super high level, retirement is just living off savings until you die or the pool of money dies. The goal is for the money to outlive your spending. Realistically, you'll probably invest that money (401k, etc) so it should be "growing" even as you draw it down. The goal most people aspire to is to have the same "income" in retirement as you did working, by having so much savings that the rate you withdraw is equal to your old salary. Thats hard to do, and when you retire you may need less money, but it's a useful goal. There are a ton of "retirement calculators" [0] that you can plug in your financial situation into and it'll output useful info... eg. if a 23yo makes 100k a year, and save 1K a month, you'll have 3.7M at age 67, but you need ~4M to "make" 100k a year for the rest of your life. I've found each calculator online makes different assumptions about stock market returns, inflation, etc, so play with a few or do some math manually. I think these calculators area great sanity check and first stop for any long-term financial plan. More concretely, you'll hear about the 4% rule - you'll be unlikely to run out of money if you only withdraw 4% a year from a pool of invested money. So if you want to retire early with an $X/yr salary, you'll need to save 25X that amount. If you're comfortable dying broke (you can't take it with you!) then you can retire with less money, but you should when it would theoretically run out.

This should give you a basic idea of your savings rate for retirement. It's just a start, but you're young so you can improve it with age as you understand your lifestyle and career, and your financials change. Oh and my advice is get as close to maxing out a 401k as possible. Its tax-advantaged, so you'll have more money than if you paid taxes on it, and since there is a yearly limit, in later years you'll wish you put more in earlier.

Beyond retirement, you'll have other expenses in life (new cars, houses, kids, weddings, etc). You should vaguely understand those costs even if you don't know which ones you'll incur and when. Weddings are expensive if you ever wish to marry (avg wedding in the US is $20k). Children are expensive too - even getting a child can be expensive if you're not able to do it "naturally" - IVF can be $25k+. At 23 you may not know if you'll want a kid or if you'll have medical trouble, but the scale of these costs would have blown away 23yo me. Then there's all the obvious childcare costs... The point is there are a lot of life milestones that a 23yo may not be thinking about but a 33yo or 43yo may wish the 23yo started planning for, so you'll want to consider saving for more than just retirement. Oh, and on top of this save for a bad day, whether thats getting laid off, or a car accident, or a sudden death, or whatever.

Thats basically it for a high-level planning - understand what your vague costs are across your life, and do the math to understand how long it'll take to save for them. You can do further optimizations for taxes, and consider the distribution of funds, or optimize the account costs structures or a million other things. First, learn the big-picture income/saving/spending trends in your life... premature optimization and all that. Personally, I think of everything in terms of the 4% rule - what can my net worth get me in terms of income via the 4% rule - eg. every 25k saved is 1k a year in forever-income.

[0] First result on google - https://www.nerdwallet.com/investing/retirement-calculator