Learn Swedish: Vargen känner marken skaka. - The wolf feels the ground shake.

This sentence uses a verb of perception (känner). When you use perception verbs like känner (feels), ser (sees), or hör (hears) with an object doing an action, the second verb is in the bare infinitive. You drop the att, just like we drop 'to' in the English translation 'feels the ground shake'.

Does känner mean 'to feel' or 'to know'?

It can mean both! Känna is used for feeling physical sensations or emotions, and also for knowing a person or a place. Here, the context of the ground shaking makes it clear that it means 'feels'. If you want to express knowing a fact, you would use the verb vet instead.

Where would I put inte if the wolf didn't feel the ground shake?

Because this is a main clause, inte comes immediately after the finite verb. The negative sentence becomes: Vargen känner inte marken skaka.

Why use marken here instead of golvet?

Both relate to the surface you stand on, but marken refers specifically to the earth, soil, or natural ground outdoors. Golvet is used for the floor inside a building. Since wolves are usually outside, marken is the natural choice.