Does GRE encrypt traffic or require a key pair, or do I need to combine it with IPSec for that level of security? What makes GRE secure?

Apologies if this is somehow against the rules of the sub. I've looked over a bunch of guides on GRE implementation and I can't find anything that actually seems to make it secure. All the IPSec guides are very clear on this - however there are no mentions of this in the GRE guides I'm following.

I know people often conflate GRE tunnels with VPN's, but from what I've seen it's just two machines that route traffic between each other and whether the traffic is encrypted or not is up to whatever else you decide to use in conjunction with the GRE tunnel.. Am I wrong here?