Ok, thanks @christian.  

At first, since there was a dot and a dollar sign, I thought there was some regexp going on, but from the link to the docs you sent, I see that it is, in fact, an expression, but an angular expression to match any value of a model and that the dollar sign acts as a wildcard. 

Ok, I'm good up to there, but again, the exact intent of this directive is still confusing

> data-ng-class="{'cc-print-hide':(!search.$)}

I'm understanding that
1. search is an angularjs filter
2. in this case, it looks like the search filter is applied to any data-ng-bind item in myfinances.activity
https://github.com/christianv/calcentral/blob/CLC-3222/app/views/templates/_myfinances.html#L214

But what would be negation imply?  I'm lost on this because it seems like it says "apply the cc-print-hide class to any item that doesn't match anything"!  Maybe it's just late for me!

Delete this comment if it seems silly.