OK well as u know here on earth we have a day which is the time taken for the earth to rotate once on its axis. a year is the time taken for the complete orbit of the sun.
on Mercury though the rotational axis takes a very long time to make a complete rotation. but the time it takes to orbit the sun is only as i said just under 88 days. so there for a year is 88 days but 1 day is a lot more.
OK ?