I heard the knowledge of bitcoin (btc)and ETH since 2016 and i want to know the difference between altcoin and BTC and ETH.
and how influential is altcoin because beginners that ask question is really or interested to know which I am willing to know.
I know some people will react to this topic violently and some will respond with manner
I don't think that people in this forum are savages and they will become abusing you for this question.
The thing you should know is that anything else besides Bitcoin is labeled as an altcoin. The reason is that probably they wouldn't exist if Bitcoin didn't exist.
To answer your question, most altcoins are an inferior imitation to Bitcoin. A few of them as Ethereum have managed to differentiate and create a use case that made them reach a higher valuation. The fact is that 99% of altcoins are going down to zero and won't ever make it. Taking into consideration all the use-cases cryptocurrencies might have I would say that a maximum of one hundred of them will be around after a few years. Consider that there are around 10,000 altcoins today.