Let me spoonfeed you /v/tard. You know how you plug your epic gaming notebook’s charger into sockets, right? Well in those sockets is voltage (110V in burgerland, some huehueland and some nippon, 230V everywhere else). But with just voltage you wouldn’t get any power (wattage). You also need amperage (amps). Now, if a short happens (shorting = unwanted discharge of power, like if you stick your micro penis into a live socket (live socket = socket with voltage in it)), all the amps start pouring out and want to get to the other side, and that usually wrecks havoc. Shorts are something you have to be prepared for (because of people like you, sticking their micro penises into live sockets, causing shorts, killing themselves, and then the company getting sued over someone’s incompetency (What is natural selection? Fuck you!)), so you design your circuits with fuses to avoid that. Fuses literally disconnect a connection (amps can only flow if the circuit is a loop = circle>circular>circuit). But how do fuses know when a short happens? Well, when short happens, all of the amps suddenly want to go through, right? So how about a device that disconnects when too much amps are going through it? Many types of fuses exist (thermal, for example, they heat up when too much amps are going through, bimetal bends one way (away from the connection = connection disconnects)). The fuse in the image is stupid, because when too many amps would be going through, the tiny copper plate would literally melt from the heat (electricity heats shit up, who knew?), making it irreparable, possibly starting fires (as melting copper would /probably/ heat the glass fibres in the PCB (printed circuit board = the green boards, very interesting to look at and not understand a single thing about for your simple mid, probably) and cause fire that could spread everywhere, burn down houses even. That is bad design.