Voip Phone numbers. Technical question

[planes]

How is VOIP different from a general landline in terms of the receiver being able to tell if the phone is either of the two.

I have participated in some off ebay activities which state that I am using a VOIP and need to use either a landline or non prepaid cell phone.

I was using Tracfone for a long time with these activities. Tracfone was letting me change numbers up to 4 times and on the last phone number switch, I got flagged and told the number was a VOIP.

Can prepaid phone numbers now be noticed as VOIP or is Tracfone switching to VOIP because they are running out of standard numbers.

With that said, what would be a go to set-up.