Hello dear Lily.
잡수세요 is honorific of 먹으세요
So it's usually used for older grandparents.
"먹으세요" This expression is the tone of an instruction. It could be used by a mother for her child or by a doctor for a patient.
Usually, people use the expression "드세요". It's a polite and kind expression.
I hope it helped!
Thank you so much for kind explaining.