I've seen the term "iteration planning" in two contexts. The first is in the context of the Scaled Agile Framework (such as this description of SAFe's Iteration Planning) and the other is in some descriptions of Scrum (such as this Rally / CA Technologies page or this VersionOne page). I have not yet found an instance of a "Pre-IPM" event, activity, or meeting.
Based on the description of getting more details about stories, this does sound a lot like what is called backlog refinement, or sometimes backlog grooming. The Rally page mentions "backlog grooming" while the current version of the Scrum Guide as well as SAFe mention "backlog refinement".
The Scrum Guide describes refinement as more than just getting details. It's also when estimates are given and the order of the Product Backlog is discussed. Typically, dependencies or relationships between Product Backlog Items are discussed to help with the ordering. The Scrum Guide does not call out a specific event for backlog refinement, only saying that the methods for refinement are determined by the Scrum Team and should not be more than 10% of the capacity of the Development Team.
SAFe also doesn't go into too much detail on backlog refinement when it's discussed in the context of a Team Backlog. It does recommend at least one refinement session per iteration or per week, but that it's not limited to a single-meeting timebox. This means should be holding at least one refinement meeting per iteration (or more frequently for longer iterations), but work for refinement may happen outside of this meeting.
One concern that I have with calling this activity a "Pre-IPM" meeting is that you may be focused on the next Iteration Planning or Sprint Planning session. It's OK to have a few Sprints worth of work refined, and I'd recommend that you should have this. If you exceed plan in one Sprint and achieve the Sprint goal early, having an ordered Product Backlog with well refined stories can let the team work with the Product Owner on getting a jump start on upcoming work. It also gives the team a preview into upcoming work that may inform design decisions. Just don't refine too much - you don't want to end up invalidating any kind of discussions or estimates about the work as the product evolves across Sprints.