Here are four images comparing the old one (on the left) with the new one (on the right):
The top-left image shows them how they look when not in use. There isn't much difference between them.
The top-right image shows how to activate the old one. There's a dongle on a spring. You press the dongle in and it springs out. You can then take it out and put it in the USB port of your laptop. When you're not using the device, the presence of the dongle switches off the power so that if you squash it in a bag, you don't accidentally turn on the laser.
The bottom-left image shows where the dongle is in the new one. You have to open the casing, exposing the batteries, and take the dongle out of a clip inside the lid. You can then put it in the USB port of your laptop. You might want to put the casing back on the device, too, so the batteries don't fall out.
Ah, but if the dongle is held by a simple clip, you can't use it as an on/off switch to stop the accidental use of the laser if the device gets squashed in a pocket or a bag or something. Not to worry, the manufacturers have thought of that: the bottom-right image shows a side view where you can see an on/off switch. So long as that doesn't get squashed into the on position, you're sorted.
I much prefer the older model.
Why is it that "new and improved" almost invariably means "new but not as good"?