Beta testing is releasing a feature to a limited group of users before it goes to everyone. You watch what happens, fix what breaks, and decide if it's ready for general availability.
In software, alpha usually means internal testing. Beta means limited external release. General availability (GA) is when it goes to all users.
Closed vs. open beta
Closed beta means you invite specific users, people who requested the feature, customers on a particular plan, or users who've agreed to give feedback. You get more targeted signal.
Open beta means anyone can opt in, often via a "try it early" toggle or a waitlist. You get more volume, but less focused feedback.
What makes it actually useful
Go in with specific questions, not just a hope that nothing breaks. "Did it break anything?" is a fine goal, but "do users understand how to set this up without documentation?" is better.
Beta users are often your highest-quality signal. They signed up knowing the feature wasn't finished, so they pay closer attention and report edge cases you'd otherwise miss.
Once you've got results, loop them into your roadmap before the full launch. Beta findings almost always surface at least one thing worth fixing before you go wide.