If the instrument ranks higher than the cash-equivalent, that instrument will be considered as a Position. The ranking here is based on the Ranking Rules that you added for this strategy.
This filter also exists as a Sell Filter, in which the Position's ranking must be lower than the cash-equivalent's ranking for it to be closed.
The way to use this filter depends on the Ranking Rules you have set for the strategy.
For example, if the Ranking Rules favor those high-gain and less volatile instruments, then this filter will only select those instruments that have higher gain (as well as being less volatile) than the cash-equivalent, because there's no point investing in something whose volatility is higher than the cash-equivalent Bonds (such as SHY) while the return is also lower; better park that money in the safe-haven of SHY.
In essence, this filter decides whether trading the instruments is more profitable than trading the Cash Equivalent.
Your strategy must use cash-equivalent (as set on the “System Settings” panel), instead of cash, to be able to use this as a Buy Filter. Otherwise a warning message is shown there:
But you can still use this as a Sell Filter even if a strategy uses “Cash”. The Positions will then exit if their rankings are lower than “cash”: