What is the difference between thoughts and awareness?

The important distinction is between what is actually happening in your mind right now -- sights, sounds, thoughts, emotions -- and your judgements and interpretations of what is happening. It is through those judgements that you distort your perception of what is actually happening. Meditation aims to clear up tha distortion.

As an analogy, you might consider how you distinguish between the external world and your judgements about it. You might think there is a yogurt in your fridge when there isn't. The thought that presents that belief to you is a real thought, but what it points to is an illusion. The solution here isn't to get rid of the thought that makes the judgement, but to distinguish between your thoughts about the external world and the external world itself, to notice when you're making judgements about the external world.

When it comes to meditation, it isn't about checking what's in the fridge or the external world, but checking what you are subjectively experiencing.

As with the fridge, people make unconscious interpretations about what is happening in their minds without realising that they're doing so. So someone might meet a new person, feel fearful, and therefore consider that person inherently evil somehow. But what they've missed is that they've judged that person to be evil based on a feeling they had. That judgement could be wrong.

Awareness has no words?

You don't need mental silence to be aware. You can be aware of what is passing in your mind in any circumstanace, whether that be few thoughts or overflowing with thoughts. Unawareness arises when you refer to your judgements about what is happening rather than what is actually happening.

Does a mental process need words to be a thought?

I don't understand what you're asking here. The sight of a cat can arise without you thinking "it's a cat", without making any distinction between the sight of the cat and the rest of what you're seeing.