"Hello"
Salary tax is a percentage taken from every salary a citizen receives from a job. It is deducted in the same money the salary is paid in (gold or local currency) and goes to the state budget of the worker's country.
Raising it sends more of every paycheck to the state budget, but workers take home less, which can make jobs in your country less attractive.
Lowering it lets workers keep more of each paycheck and can attract more workers, while the state budget collects less from salaries.
This is a neutral explanation to help you decide — it doesn't favor either side.