the use of the auxiliar DOES?
A multinational firm must be aware of how the regulations might change in the markets it DOES serve as well
as those it may desire to serve in the future.

A multinational firm must be aware of how the regulations might change in the markets it serveS as well
as those it may desire to serve in the future. (Do the above two sentences have the same meaning???)

PS: I know the use of do/does/did and so forth but I don't know why it is used in this context

Question

the use of the auxiliar DOES?
A multinational firm must be aware of how the regulations might change in the markets it DOES serve as well
as those it may desire to serve in the future.

A multinational firm must be aware of how the regulations might change in the markets it serveS as well
as those it may desire to serve in the future. (Do the above two  sentences have the same meaning???)

PS: I know the use of do/does/did and so forth but I don't know why it is used in this context

Answer

The auxiliary 'does' when used in affirmative sentences in this way serves to emphasise, contrast or contradict.

In this sentence it is highlighting those markets which the firm currently serves. Or in other words, not only does the firm need to be aware of how the regulations might change in the markets it may desire to serve in the future, but ALSO those which it is already serving at the moment. The use of the auxiliary emphasises this contrast.