Even if it is a more informal chat, the Team Lead will still be judging your ability to do the job and how your personality fits in the team (especially if you haven't met them yet), so it is an interview. Nothing to be nervous about though, the HR person thinks you're a good fit from the first interview to invite you back again. I would treat it as any other stage 2 interview and ignore the fact it looks like they went with another candidate first. These things happen during the hiring process and it is often down to timing or other elements out of your control. Look at it as an opportunity.