That's a MCB ('miniature circuit breaker') inside a consumer unit. Although I think officially it's called an MCB, people often call them RCDs (residual current device) in everyday life. To describe the issue in England you would say that an MCB in the consumer unit keeps on tripping ('fuse boxes' used to be used instead of 'consumer units' so you might hear that name, too). So, for example, you can say: "Hello, I've got a problem with the electrics in my house and I was wondering if you might be able to help me please. The problem is that an MCB in my consumer unit keeps on tripping and I have to keep on resetting it. I'm not sure if there is a fault.". If they don't seem to understand, you may want to say that an RCD keeps on tripping or "I've got a problem with my fuse box. A fuse keeps on tripping," instead, even though these are technically incorrect. You cannot just ignore this issue, it indicates there is a fault. I would contact an electrician.

That's a circuit breaker. You are "flipping the switch back on" every day. Take this as a danger signal. Find the source of the problem and fix it. If you cannot determine where the circuit is being overloaded, don't take any chances. You need to call an electrician. Otherwise, you could start a fire!

1) Brian Sewart pointed out that the breaker could be faulty. I notice something odd in the picture. The breaker that has tripped says "B10" and all the others day "B20." Maybe it is the wrong kind of circuit breaker. Unfortunately, this is a job for an electrician. An electrician should look at the wiring and decide if "B10" is really right. Maybe the wiring is enough for 20 amps and it could have a 20 amp circuit breakers. Where I live, this would be about a $100 job for an electrician. 2) The next time it happens, don't reset the breaker right away. First, unplug everything that has lost power before you reset the circuit breaker. Look at them all. Try to find a little plate that says something like "8 A" for eight amps, or "5 A" for five amps. Try to figure out which ones are the ones that draw a lot of current. See if you can plug them in somewhere else, on a different circuit.

As others have noted, a circuit breaker trips when a circuit is overloaded. A circuit breaker does the same job as a "fuse." "Overloaded" means you are drawing too much current. Without a circuit breaker, the wires inside the walls would get hot and might start a fire. If this is a 10 amp circuit breaker, and all the things plugged into that circuit draw a total of 15 amps, that's too much. The breaker will trip. When it trips, everything that is on that circuit will lose power. You said "set it up," meaning push the lever up. The natural way to say this is to say "I need to reset the breaker." If everything is still plugged in and turned on, as soon as you reset the breaker, they will all start drawing current again. They will draw too much current and the breaker will trip again. If this is happening, you need to unplug some things before you try to reset the breaker. You need to start with the things that draw the most current. Things that draw a lot of current include heaters, or any things that get hot (like irons or hair dryers). Things with big motors in them, like air conditioners, draw a lot of current when they are starting up. You need to plug them in somewhere else.

"One of our circuit breakers trips several times a day."