well the difference is that the Executive is the one who has the role of execution. so whatever the manager ask him/ her to do he/ she executes (as the name itself suggests and the hierarchical level goes).... Manager is the person who has the power to manage and put the resources to use in correct way and time. whereas his assistance is der to help him in all the possible ways. hence the manager may be the person with specialized stream of HR like HR Recruitment Manager, HR T&D Manager, HR Talent Acquisition Manager, etc... now coming to Generalist, this profile has the hand on the entire HR gamut, where it may start from recruitment and covers administration, legal compliances, strategic HRM, Performance Management, etc. the HR Officer is the synonym to the the HR Generalist but widely been used in PSUs' as they have a defined hierarchy under the Govt. guidelines. Hope it explains the difference well. Thank you.1 Kindly add into my know how as well if any correction is required.
2nd September 2016 From India, Mumbai