Hi Brian,
I would recommend you speak to your accountant for more details, however the basics are that there are Physical Nexus and Economic Nexus. Physical Nexus is anywhere you have a physical presence, inclusive of where you are shipping from, your office location, etc. Economic nexus kicks in for the areas where you don’t have Physical Nexus. In particular, while when you start you will likely have no tax obligation to any states that you do not have a physical presence, there are revenue thresholds that once you sell a certain amount, the state will expect you to start paying taxes. For example, if you sell to customers in California, once you reach $500K in sales, California will expect you to start paying tax.
If you use QuickBooks Online, they do a decent job helping to manage this for you as long as you setup your addresses properly.
For some more information, feel free to check out our guide here, which also includes a link to more details from QuickBooks: https://community.weintegrate.co/t/what-is-tax-nexus-and-how-does-it-impact-me/188