Is Activator and Hardener the Same Thing?

From a general standpoint activators and hardeners do the same thing; initiate cure of 2K products. However, you must use only the activator each product calls for on the tech sheet and not interchange hardeners/activators from different brands or products.

Is activator and reducer the same thing?

Activators: activate the curing cycle. They come in different speeds: slow, medium, fast for use in different temperatures. Personally I use slow activator all the time. Reducers: reduce (old term was thin) the activated products.

What is an activator for paint?

In the auto paint world, activators are synonymous with "hardener" or "catalyst". Both help the basecoat or clear coat to cure and harden, preventing bubbling or fading while also helping to protect against weather or chemicals.