i mean how could there be a overload or a short, my battery always provides 12v(roughly)?
There are just too many ways to create a short or overload. Here's a few I've experienced:
Motor windings overheat and short together.
A component fails and shorts internally, caps, ICs.
A cap or IC is wired or inserted backwards.
Two wires get pinched together, cutting through the insulation and shorting.
Slipping with a screwdriver or other tool and shorting two contacts.
Connecting the wrong wires together.
Miscalculating a resistor value or misreading a resistor value that draws way too much current when the circuit is turned on.
Yes the battery will try to provide 12V but at what current? What happens when the load becomes close to zero Ohms? Hint: use Ohm's Law to calculate I. Then what happens at the battery?