Concentrate Straws (aka wax straws, nectar straws) are a subset of wax pens that have the following difference:
Unlike a dab pen, the wax isn't placed inside the atomizer (coil). Instead, the coil is on the tip of the device, and once hot, it is placed into a shallow dish of wax to melt and vaporize the material. The vapor is inhaled through a small opening in the tip and up into the mouthpiece, hence the name "dab straws."
Concentrate straws are a little easier to use than dab pens since you don't have to worry about loading your wax into them. However, you do give up some portability with concentrate straws as you'd have to carry the jar with you.