A circuit is defined as a circuit breaker (often a double breaker with tied handles) and all the outlets and hardwired devices that it controls, i.e. that lose power if you switch it off.
Obviously, some circuits are failing, and whole circuits are failing at the same time (that is, all the outlets/devices on the circuit at once).
So I need you to identify the failing ones. Often if your panel is properly labeled as required by law, this won't be too hard.
Cut up some Post-It notes to make flags, and stick the flags on the breakers that are failing. Then, shoot us a photo of the panel face. Also if possible the label that describes the make/model/instructions of the panel, and the breaker labeling chart if any.
Do this before you call in an electrician. This may be free to fix.
What I want to see is if all the failing breakers fall into a pattern that looks
If it does follow this pattern, then this is almost certainly a power outage from the power company. This is what power outages look like. "Why doesn't the power fail completely? Because in North America, power is delivered as 3 wires. Typically 1 wire fails. 2/3 chance it knocks out half your panel. 1/3 chance it causes a floating neutral which makes your voltages go bananas.