That means that if you wanted to create a multi-stage form, instead of displaying a “thank you” message you could redirect the user on submit to your second form, and append whatever personalization tags you wish to prefill, for example activecampaign.com/forms/2?email=%EMAIL% (link pictured)
I did this thing once but it was a long-ago before I found out about AC. For such a purpose I created two URL’s that actually had been scripted form I took from here https://990-pf.pdffiller.com/ It worked quite fast so I left this thing as is. It’s also easy to do with the very AC as well but this way would come in use to you if you have some projects ain’t connected to your account