Time Stop is a Power in BTD6. It temporarily freezes the screen for 10 (?) seconds. All bloons are reduced to 10% of their original speed but all towers' attacking speeds are reduced to 30% of their original speed. Before the 11.0 update, everything on screen would stop moving (this includes bloons AND towers). However, both of these versions of Time Stop will offer the player additional breathing time in order to change defenses, allowing players to decrease stress levels while doing so. It can also be used to refresh cooldowns of towers when they're not available. It should be noted, however, that Time Stop will not affect BADs at all.
In preparation for Co-Op Mode, and also due to the pauses that pressing the menu button provides in normal games, Time Stop was reworked to act as a superior slowdown. However, this purpose is defeated in the case where BADs spawn, since they are now fully immune to the Time Stop's effects.
Bloons now move at 10% of their normal speed during Time Stop
Tower attack rates and move speeds are reduced to 30% of their normal rate, which overall should means they attack around 3x faster than the bloons move.
Tower ability cooldowns now function normally instead of fully stopping
For some reason, the 11.0 change made the ability no longer affect B.A.D.s, meaning that using Time Stop against a B.A.D. actually makes the defense weaker. It is unknown if this is a bug or intentional, but this shows that Time Stop is probably uses a slowing similar to Bloon Sabotage.