The mirror of equal-highs. Longs who bought near the level place stops beneath it, and breakdown traders place sell stops there, so the area below is dense with sell orders waiting to trigger.
A sharp poke beneath equal lows that immediately reverses is the classic failed-breakdown and is one of the more repeatable patterns in the price action literature, because the stops that fired become buyers again when they are forced to cover or re-enter.
As always, a break below equal lows that continues is just a downtrend continuing. The pattern is only useful with a rule for what counts as reclaim, for example a close back above the level within a stated number of bars.
Related: equal-highs, failed-breakdown, liquidity-sweep, double-bottom, support