In the beginning, founding teams only really need 2 things; 1) building and 2) selling (that includes marketing). Decide which one you are, and then assume you'll be doing that all day, along with miscellaneous stuff like fundraising, finding office space, customer support and hiring (amongst other things).
Being a founder is great if you love being thrown in the deep end and having to figure everything out. You will have to wear every hat at some point and face constant doubt and ambiguity. You will learn and grow immensely, maybe make a lot of money and perhaps even "make the world a better place".
Chances are you think being a founder is sexier than it is thanks to the media. In reality, it's incredibly stressful and high-risk and you'll probably be happier doing something else. If your core motivation for starting a company is to prove something to yourself or to make a lot of money, then there are probably better ways to do both.
Not all founders are VC backed and trying to build unicorns. There are a lot of other founding paths that are often lower risk, lower stress and still high enough reward that you'll grow a huge amount and never have to work again if you do well. What if you set out to build a $10m business instead?
Depending on how many co-founders you have and the terms on which you raise capital, you will probably own at least 20% of the business when you start it. This is the highest reward you will find in any role, but also the highest risk.
Founders learn to wear a lot of hats and get sh*t done. You will level up significantly as an operator, and if things work out you'll continue to grow with your business. If things don't work out, a lot of companies value the skills founders learn and will be fighting over you for senior roles.
Founders who go back to working for other companies often find themselves in senior positions managing product, sales or operations teams.
You'll spend time talking to investors, customers, candidates and partners as a founder. If your business does well, you'll find a lot of people coming to you organically as well.
Your business will likely consume you. You'll work long hours and find yourself thinking about work even when you're not working. The only thing stopping your business running out of cash and dying is your ability to execute faster.