The Oxford Learner's Dictionaries are an excellent resource. You can even listen to recordings of the words. tea noun BrE /tiː/ ; NAmE /tiː/ https://www.oxfordlearnersdictionaries.com/definition/english/tea?q=tea teeth plural of tooth BrE /tiːθ/ ; NAmE /tiːθ/ https://www.oxfordlearnersdictionaries.com/definition/english/teeth?q=teeth

Unvoiced doesn’t mean silent. Arabic has a voiced “th” as in ظ and unvoiced as in ث. English has a voiced th (as in “this”) and an unvoiced (as in “thought” or “teeth”). Of course, it’s hard to tell in English because they are both spelled the same. I hope that helps.

No, they don’t sound the same. The “th” in teeth makes the same sound as ث in Arabic.

Like what they have said, just because it is unvoiced doesn't mean it is silent. Or, it could be "silent" if you are 30+ meters away from the speaker. xD

As Christi says, "unvoiced" doesn't mean silent. It means that you make the sound by pushing air through your mouth, without using your vocal chords. (You use your vocal chords to make vowel sounds and "voiced" consonant sounds.) For example, the sound "g" is voiced, but "k" is unvoiced. You make the two sounds with the same part of the mouth, but when you say "g" you use your vocal chords, and when you say "k," you only use a puff of air. The sounds "b" and "p" are also very similar, but "b" is voiced, and "p" is unvoiced. The sound "d" is voiced, but "t" is unvoiced. The sound "v" is voiced, but "f" is unvoiced. The sound "z" is voiced, but "s" is unvoiced. Try making these pairs of sounds, and you may be able to understand the idea of "voiced" and "unvoiced" more easily.