A record of where upward or downward relocation stopped — not a resistance or support level with inherent holding power.
Full Explanation
A prior high is simply the price where upward relocation stopped at a specific moment in time. It marks the point where sell-side liquidity was sufficient to absorb the buy aggression arriving — or where buy aggression ran out. It is not a resistance level in any inherent sense. When price returns to a prior high, the only relevant question is whether sufficient opposing liquidity exists there right now to absorb the current aggression. The prior high tells you where the interaction happened before. It tells you nothing about whether a similar interaction will happen again. Lows work identically — a record of where downward relocation stopped.