There probably is a reality, in that there are experiences that people can share and can compare their understandings of. If I meet some people in a room, we can agree where the lights are and whether they are turned on. However the meaning and nature of that reality is definitely interpretive, and thus the nature of any collaborative experience (community, society, relationship, company) exists between the individuals and is mutually formed by their agreements and debates. But this also serves as input onto their perceptions of themselves, the others, the interactions, and thus informs the behaviour reflexively.
We define ourselves in terms of our direct agency first, and second in relationship with the other people and objects we encounter in exercising that agency. All categorisations of things are arbitrary (though as above, they are more or less agreed upon). But we usually have an idea of what is “me”, what is “others”, and what are “things”. Beyond the physical we define ourselves by the nature or traits we either believe ourselves to demonstrate, or would like to think we would demonstrate. If I think of myself as “generous”, that might mean more that I would like to believe I would treat property selflessly than that I actually have done or am currently doing.
With this in mind, a researcher and a participant work together to uncover or to form an understanding of the researcher’s inquiry that exists between them. It cannot be “reality” because the discovery is mediated by the interaction between researcher and participant, and it cannot be purely the participant’s viewpoint as that viewpoint is both adapting to and shaping that of the researcher.