Okay kiddo, so an assessor is like a judge who decides how much a property or anything else is worth.
Let's say you have a toy car and your friend has a doll. Your mom wants to know how much each of these things is worth, so she asks the assessor to come and take a look.
The assessor will look at the toy car and the doll very carefully and think about how much they cost when they were new, how much they've been used, and how much people would be willing to pay for them now.
Then, the assessor will decide how much the toy car and the doll are worth and tell your mom. This is important because if your mom wanted to sell the toy car or the doll, she would know how much to charge for them.
Assessors don't just decide how much toys are worth, they also decide how much houses, cars, businesses, and even land are worth. It's an important job that helps people make fair deals and agreements.