In this audio lesson, you are about to learn the terrible mistake of many students and the list goes to advanced level.

The real deal is when the word ends by " ed ".  So, should I consider it as simple past tense.  

Based on my explanation, if you talk about a verb, so it is the simple past tense.

Now if it follows this sequence " subject + verb to be + word+ed " so, it is an adjective.