A welding shop, a greenhouse, a craft booth — they all have one thing in common. The people who already trust you are worth more than any new audience you could chase.
But if the only way past customers can find you again is by remembering your name, or happening to scroll past your post at the right moment, you're leaving good work up to luck.
What a customer list actually is
It's just a list of people who said yes, keep in touch — usually an email address, maybe a name and what they bought. Nothing fancy. A spreadsheet counts.
The point is that it belongs to you. If a social platform changes its rules or disappears tomorrow, your list still works.
A small next step
Start collecting emails this week. One notebook by the register, or one line on your quote form. That's enough to begin.