What do "the costs of recruitment or contracting" mean in the Federal Decree-Law No.33?

Dear sir/madam,

I want more explanation of clause 3 of article (9) of the Federal Decree-Law No.33 which states the following:

If the worker wishes to move during the probationary period, to work for another employer in the State, he shall notify the original employer of the same in writing within not less than one month from the date of his wish to terminate the contract. then, the new employer shall compensate the original employer for the costs of recruitment or contracting with the worker, unless otherwise agreed upon.

What do "the costs of recruitment or contracting" mean?