Why is my electrical outlet not working?
Assuming that outlet has been working fine and there were not recent catastrophic events or construction that has taken place, you likely need to reset the circuit.

First check to see if there is an ongoing regional power outage. An easy way to check for this is to see if the power is working elsewhere in your building or neighboring buildings.

If the outage is localized to a portion of your building, you may want to check the following:

If the outlet is a GFCI, you will need to find the main outlet in the circuit and push the reset button on it.  GFCI (or GFI) outlets are common in locations where water is present, for example in kitchens and bathrooms.

If the outlet is not a GFCI outlet or if resetting the GFCI outlet had no effect, locate the circuit breaker for your building and check if any of the circuits have been tripped.  You can identify a tripped circuit when you open the panel by looking for the one of the circuits in the panel that is not in the same orientation as the others. Fix it by flipping the switch to match the others.