An attempted break-in is an attempt to open a door, a lock or a shutter without a key that did not succeed. They did not get in, but they tried.
It does not always leave obvious damage. Be suspicious if the key goes in or turns differently, if there are new scratches around the cylinder, if the escutcheon has been moved or if the frame has a notch at the height of the latch. On a shutter, if the bottom slat is marked or out of its guide rails.
Even if the door still opens, it is worth having it checked: a damaged cylinder can fail just when you need it most. Call the police, take photos and, if you need it for the police report or the insurance, we give you a forced lock report.