First don’t be intimidated by the negative haters out there talking down about DMR, just because they can’t understand it or figure it out they trash talk DMR. If you can study and get a ham ticket you can learn DMR. Once you're on DMR you'll be rid of those negative people.
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DMR stands for Digital Mobile Radio or in the industrial radio world Mototrbo. DMR utilizes TDMA frequency splitting where a single frequency is split into 2 usable channels; these 2 are called time slots, there are only 2 time slots. Theoretically you can have 2 simultaneous conversations going on at the same time on a single frequency. Think of time slots as the A & B side of a dual band full duplex radio. DMR uses color codes to gain access the same as a PL tone is used. If you have the correct color code you can access the DMR repeater.
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Most DMR repeaters and hotspots run on UHF hotspots run in the 430 range although there are some dual band models that will do 2m.
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What is a ham radio MMDVM hotspot? "MMDVM" stands for Multi Media Digital Voice Modem again a fancy for for a device, basically its a small little digital repeater capable of running all digital modes used by hams.
It consists of a raspberry pi and an MMDVM hat, that's the modem and transceiver
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A hotspot gives you the freedom to connect to anything you want, when you want, for as long as you want. You won't be tying up a repeater or a time slot, you can park on very busy talk groups and not bother anyone. Most repeater owns do not allow their repeaters to connect to a really busy talk group like 91, 93, 3100, 313136 because of the heavy duty cycle strain on the machine. MMDVM repeaters are usually FM analog mobile radios or repeaters with an MMDVM hat interface that turns the old school FM analog repeater into a multi mode digital repeater, capable of running more than one digital mode like your hotspot. MMDVM repeaters are very popular because of the cost effectiveness and the flexibility. Motorola TRBO and D-Star repeaters are expensive and require expensive CPS programming software and cables. I have 3 MMDVM repeaters local to me that run DMR and D-Star, I use them both in both modes and you can't tell the difference.
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DMR networks, the biggest is BrandMeister, a global DMR server web with servers all over the globe. There are 3 USA servers, San Jose / Chicago / and Dallas. DMR repeaters connect to any of these servers and traffic from them is sent to all servers worldwide. Calls are routed using talk groups, a series of numbers that correspond with a group or geographic region or individual user. For example to call Arkansas statewide you would use talk group 3105, to call on Little Rock Metro you would use talk group 310501. To call your friend you would just use that person's DMR ID, the 7 digit number assigned by radioid.net. You can also have a private one on one conversation with another DMR user that can not be monitored by other users.
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Other network include

DMR+ IPSC2 Global Master Server List    DMR+ IPSC2 "QuadNet"    XLX    TGIF   AmComm     QuadNet System-X    FreeStar    FreeDMR    System-X


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Hoseline is a web-based application that streams audio from talk groups on the BrandMeister network. You can monitor it kind of like Broadcastify only it's free with no annoying ads. Currently it's the only network with this kind of remote monitoring.

You can use a DMR capable repeater or a hotspot, there are many types of MMDVM hotspots, the most common is the pi-star hotpots consisting of a raspberry pi and the MMDVM hat. These little devices are like having your own little low powered personal digital repeater capable of other digital modes like P-25, NXDN, DMR, D-Star. Basically what a hotspot allows you to do is talk anytime to anywhere you want from the comfort of the recliner using a low powered HT. They are connected to the DMR servers directly. If you’re lucky enough to have a DMR repeater close by you will still need to share it with others and most repeater owners frown on tying it up on a busy talk group like 91 worldwide or 3100 USA nationwide causing full duty cycle strain.

Programming most DMR or other digital radios requires  the use of CPS programming software and a cable all done on a Windows based computer. The parameters and all the configurations that run the radio are called a code plug, just a fancy name for a programming file for the radios with the frequencies and talk groups. Programming DMR radios is a lot of redundancy, adding the same repeater info over and over each time you’re adding a talk group, example below.