What does this icon with a dart and two stars stand for in Bloons TD 6?

This icon is present on a few of my maps, indicating the same three towers, a Village, a Spike Factory, and a Wizard Monkey:

I can't for the life of me figure out what it means though?

That's the symbol for Monkey Teams. You get extra money if you beat the level using only those towers.

Another symbol you'll sometimes see on that screen is the Golden Bloon, which sometimes launches a special, extra-tough bloon that gives extra money for defeating it.

You'll never see both specials on the same level. According to the wiki,

[Monkey Teams and Golden Bloons] will alternate every 2 days, every two 8:00pm NZST days to be specific.