Ms. Word for Mac

if I get MSWord for Mac, will I be able to do all Word applications on my Mac without any confusion? Will work saved on Word on my Mac then be readable to others using a HP or something?
I ask because although I am set up with Pages, I see that I can save as a word doc, but I have been informed by someone using a non-Lac that they could not open it. Just very confused and I will soon be sending out resumes for job applications and don't want a mess up. But if Pages saved as docx should actually work fine, then I'd rather not splurge on Windows for now.