I know that those ribbed seals can come from an ultrasonic welder - it has a ribbed wheel that is run along the perimeter of the packaging. Material looks like PVC.
If you don’t see the ribs on the seal it’s probably a heat bond - that’s what they use for most plastic bags and ziploc bags.
I personally like ultrasonic welding - it’s fast, uses less energy and may add to a professional appearance.