If you're a DIY enthusiast, greasing your trailer or RV axle is a standard afternoon task. Here is the basic workflow: How to Grease a Trailer Axle - Lippert

Not all grease is created equal. Depending on what you drive, you’ll need a specific type:

Tractors and loaders often have specific "grease points" (zerk fittings) that require heavy-duty polyurea or lithium complex grease to handle rugged terrain. Maintenance 101: How to Grease Your Axle

At its simplest, axle grease is a thick, heavy lubricant designed to reduce friction between moving parts in your vehicle's axle assembly. Unlike engine oil, which is thin and flows freely, grease is "viscous"—it's designed to stay exactly where you put it, even under extreme pressure and heat.