sit at/at the table

I’m reading this book entitled Common Mistakes in English published by Longman. I saw this there. It gave examples about school which says ‘go to school’ means ‘attend school as a student’ while ‘go to the school’ means ‘visit it’ and church which says ‘go to church’ means ‘go and pray’ while go to the church mean ‘go and visit the church’.

Then it put a note at the end which briefly says, ‘Similarly, distinguish between go to bed and go to the bed, sit at table and sit at the table…’

What’s the difference between ‘sit at table’ and ‘sit at the table’ in meaning?