You will only be able to access your State Pension at your State Retirement Age, which depends on your date of birth.
However, if you have a workplace pension and/or other pension pots, you may be able to access your other pension savings at the age of 55 (although this is set to rise to 57 over the next 4 years).
Some people choose to do this in order to:
Reduce their working hours as they get closer to retirement
Prepare for retirement, for example buying a new house
Support their family