I don’t know why these still exist when you can use a smartphone as a hotspot and not have to pay for another line.
Having an additional hotspot takes the load off your phone for battery life and allows you to not require your phone to be in the area if others are using your hotspot.
Full disclosure I looked for a gif that said “and it’s back”, but this one came up first. If I need a hotspot I use my phone, but some people have a use for this. Go sports!
Why is his food still moving?
It makes sense if you are traveling overseas using a local SIM. Otherwise I use my phone as being more secure and plug in an AC adapter charger. Never into a public / airport USB or airplane port which are notorious for being purpose designed or modified to download your phone contents and passwords.
I purchased this last time and don’t know how to use it
Well, for one - you plug this in, stick in your glove compartment or center console, and everyone in the car can connect their phones and/or tablets to it. You can also connect your DMR hotspot to it.
You can also use it in your hotel/motel room.
Most cell phone plans have ridiculous data restrictions on the amount of hotspot data you can use. This keeps you from having to worry about hitting that limit, and what you will do once you hit it.
I don’t have this particular one, but I used another when I was in a skilled nursing facility for 3 months after a surgery. I used it for my radio hotspot, my phone, tablet, and the room TV which happened to be a ROKU smart TV. You never know who might be spying on the “free” WIFI when you are out and about - better to use your own.
Do you have to purchase WiFi service?
@Wooter708237553 and @wootsboc - You have to purchase a GSM cellphone service plan. Or use the GSM Sim in your phone in the hotspot device. If your current phone uses CDMA then yes you are going to have to purchase another cell plan.
If traveling overseas, buying a local GSM Sim maybe the cheapest option. Using your phones GSM Sim May incur horrendous charges.
But for within the US usage though including any travel out of state, many of us are saying that just using our phone as a hotspot and charging it at the same time works well.
Hope this helps. And happy anniversary cake day @Wooter708237553 ! 
Thanks. I would have a use for this here in the USA but I don’t know where to get cheap service with a sim card that would fit/work with this device.
Recommendation accepted
I bought this last time. I use a Tello SIM with it. It’s more of a backup but service is cheap to keep it active. With Tello I’ve found that if you manually buy the next month’s service instead of waiting for the auto pay, the unused data rolls over. Otherwise, with auto pay it restarts each month.
Where I use it is in the work truck. The phone is connected to Android Auto. When it is, the hotspot on the phone won’t work properly. This is a separate connection and works fine, plus the battery life is great for standby.
Good Tello tip!
AT&T does charge extra/month for allowing me to use my phone as a hotspot.