* Gravity is always present: Every object with mass has gravity, and it pulls things towards its center.

* Buoyancy is a reaction: Buoyancy is an upward force exerted by a fluid (like water or air) on an object submerged in it.

Here's the key:

* Whether gravity is "stronger" than buoyancy depends on the object and the fluid.

Examples:

* A rock in water: Gravity pulls the rock down, but the water pushes back up with buoyancy. If the rock is dense enough (its weight is greater than the weight of the water it displaces), it sinks. Gravity is stronger.

* A boat on water: A boat is designed to displace a lot of water, making its buoyancy greater than its weight. The boat floats. Buoyancy is stronger.

* A balloon filled with helium: Helium is lighter than air. The balloon displaces more air than its own weight, creating a net upward buoyant force. The balloon floats. Buoyancy is stronger.

In Summary:

* Gravity is always present, pulling objects downwards.

* Buoyancy is an upward force from fluids.

* Whether gravity or buoyancy is "stronger" depends on the object's density and the fluid it's in.