[Grammar] Past participle 'ed' adjective VS Passive verb VS past tense

[need help]

Can anyone give me explaination between Past participle 'ed' adjective, Passive verb and past tense..
I don't know to distinguish all of that because it is all use 'ed' at end of the word
And I hope anyone can give a note on how and when should to use this 3 kind of verb.

 

[5jj]

I needed advice. - Past tense. 'Needed' is clearly functioning as a verb, and there is no auxiliary.
I have needed that for some time. - Present perfect. It is constructed with the auxiliary HAVE and the third (past participle) form of the verb.
I must go. I'm needed at the front desk. -Passive Voice. It is constructed with the auxiliary BE and the third (past participle) form of the verb.
I took a (much) needed rest. - The third (past participle) form of the verb is used as an adjective.

It is often not easy to say whether the third (past participle) form of the verb after BE is functioning as part of a passive-voice construction or as an adjective. It doesn't really matter much.