What Moon does in a chart
Moon is the part of the chart that answers one question:What do I need in order to feel safe? It describes emotional needs — not events, and not outcomes.
What Pisces does to it
Pisces is a water sign, so it moves on feeling and atmosphere. It is also mutable, which means it adapts things. Put those together with Moon and you get needs to merge — porous, imaginative, merging, applied specifically to emotional needs.
Pisces is ruled by Neptune, so this placement tends to be coloured by imagination and idealism as well.
The useful version
Placements are not verdicts. This one describes a default setting, not a limit — the things listed above are what you do when you are not thinking about it, which is exactly why noticing them is worth something.