The purpose of the ResearcherID is to help disambiguate authors with similar names and/or similar research areas. Persons with common surnames (Johnson and Smith are common in the United States, Li, Zhang and Chen are most common in authors from China according to http://www.mandarinhouse.com/100-common-chinese-family-names) may wish to create a ResearcherID profile and put citations to their works in the reference lists.
You may use your university email and whatever password you've created to login to Web of Science and EndNote Basic to login to ResearcherID's system.
Note: Recent changes in the relationship between ORCID and Thomson Reuter mean that ORCID is feeding their data to Web of Science. This may mean that ORCID will replace Researcher ID as a disambiguation tool.
ORCID is another type of identification code for researchers. They are not mutually exclusive; in fact, if you have a ResearcherID it makes it even easier to make an ORCID. As noted above, ORCID has begun to share data with Clarivate Analytics, so you may not need to create a Researcher ID. ORCID is developed by a nonprofit group supported by various academic institutions and publishers.