Perfect to learn on without needing to use money.
They're an incredibly skeezy company and if memory serves me right actually are one of the extremely few ccTLD registrars to get fined for mistreating customers (which is extremely uncommon, ccTLD registrars have kinda free range to do whatever they want generally speaking).
In a more direct sense, they stole several domains from me about a decade ago by marking my account as abusive and then tried to resell those domains for ~6.24 euros to anyone else as a "premium" domain name (which I figured out when I made an alternate account) once they got some slight amounts of traffic. Very scummy.
It's a free provider so these aren't unexpected shenanigans, but I'd still advise anyone looking for a registrar to not use Freenom. Go for a dynamic DNS provider instead if you're starting out, there's quite a few with free plans. If you're willing to throw a few bones for a proper domain name, I'd recommend Porkbun myself but there's other options too.