what is Jira , tickets and where to find an issue?

Im totally new to this platform.So can anyone explain me what is JIRA, what are tickets? Working upon what can I find an issue?

@nischalvangipuram Did you get a chance to look at this http://devmanual.openmrs.org/en/…I believe the answers you want are in that book especially this page http://devmanual.openmrs.org/en/Community/collaborationTools.html Otherwise welcome to the community…We are looking forward to your contribution.