The domestic electricity supply in the UK is alternating current (a.c.). It has a frequency of 50 Hz and a potential difference of about 230 V.
A frequency of 50 Hz means that the supply completes 50 full cycles every second. In 2 seconds it completes 100 cycles. Each cycle has the current flowing one way and then the other way.
The mains voltage of about 230 V is far larger than the 1.5 V of a single cell, which is why mains electricity is so dangerous and why mains appliances must be used with care.