If you've worked for another company or business and then retired after years of working with them and are receiving a pension that the employer or yourself has contributed too then yes you can then go back to work either full time or part time if you so desire and still collect that pension.
Pensions differ from social security. With social security you can still work full time and collect your social security benefits once you reach full retirement age.
But with a pension you can work and still receive your pension payments even before full retirement age.
Some people do choose to go back to work either full time or part time after retirement to keep busy when they find that they're bored in retirement.
Usually though they'll go back to another job or they'll start there own business in retirement.