What gets the electricity into a computer?

Typically computers are connected to a UPS. Rarely they are connected to direct power supply. The UPS may provide 110V or 220V supply oscillating at 50Hz and 60Hz. These values depend on the particular country's power supply standards. The electricity supply then goes to SMPS in case of desktops. SMPS is a control circuit that switches the load current rapidly on and off in order to stabilise the output voltage. Typically different components get different levels of voltages. It may range from 1.5V to 12V. Note that computer components run on DC supply not AC supply so it is converted by SMPS.

In case of laptops the AC supply is converted to DC and then given to battery which further supplies the laptop components.