How does this collar correct barking?

It is an automatic no-bark collar: a sensor picks up the bark and the unit delivers a correction on its own. There is no remote, so you cannot trigger or adjust it by hand.

It is sold in one size, so measure your dog's neck before buying. Small breeds and large dogs with thick necks are the likeliest to have fit problems.

Can I set how strong the correction is?

No adjustable levels are listed. The collar works automatically at whatever setting it ships with.

What battery does it use?

The listing does not state the battery type or expected runtime. Check the unit for the battery compartment before you rely on it for long days.

Is it safe to leave on my dog all day?

No-bark collars are usually meant for supervised training sessions, not all-day wear. Take it off when you are not watching the dog and rotate contact points to avoid skin irritation.

How is it different from a remote trainer?

A remote trainer lets you correct at the moment you choose, at a level you set. This collar fires only on barking, so it cannot help with recall, jumping or other commands.