What are the benefits of having foreign workers in a country?

There are
benefits to both the country where the foreign workers work and the countries from which they
came.

In terms of the host country, the benefit is cheaper labor.  In many
developed countries, natives do not want to do the hardest, dirtiest, and most dangerous jobs
for the relatively low wages that such jobs usually pay.  This means that a class of jobs will
likely go unfilled unless foreign workers are brought in.  Alternatively, the wages for those
jobs would have to rise high enough that the price of the product made would end up being too
much for most consumers.  For example, if people who kill, clean, and cut up chickens were paid
high salaries to make up for how unpleasant the job is, the price of chicken would go up a great
deal and consumers would buy much less of it.

In terms of the country of
origin, the benefit is remittances.   This is the term for money that is sent home by citizens
of the country living abroad.  For some countries that have a lot of citizens working in foreign
countries, remittances can be a major part of national income.  The remittances can be used to
boost local economies and move the countries towards a higher level of development.

In these ways, the practice of having foreign workers in a country helps both that
country and the country from which the workers came.