Learn Spanish (Latin America): El sendero está mojado y resbaloso.

We use está (from the verb estar) because we are talking about a physical state or condition of the trail right now. It is currently wet and slippery. If we used es (from ser), it would imply that being wet and slippery is a permanent, defining characteristic of the trail, as if it were made of water!

Is mojado a verb or an adjective here?

It is acting as an adjective describing the trail, but it comes from the verb mojar (to wet). Many Spanish adjectives are formed from the past participle of a verb. Because it acts as an adjective here, its ending changes to perfectly match el sendero (masculine and singular).

I've seen a different word for "slippery" before. Is resbaloso common?

Yes, resbaloso is the most common way to say "slippery" in everyday Latin American Spanish. You might also encounter resbaladizo in formal written Spanish or in Spain. Both words come from the verb resbalar (to slip).

How would I connect this sentence to the aunque (even though) grammar from our current lesson?