Bitcoin is the center of the cryptocurrency market, its like the dollar of the world where many local currencies are depending to its market.
While altcoins, it means alternative coins. They are coins that has been modified and created which is inspired through bitcoin and they have their own network/blockchain as well. You cannot send bitcoin directly to any altcoin and the popular use of altcoins today are becoming the exchange of bitcoin to profit.
Thank you for your immediate response sunsilk! And also for the clarification. I thought that Bitcoin are two different cryptocurrency, but it turns out that it altcoin is also bitcoin and the only difference is it is modified.
Don't mention it.
Bitcoin is the only one supreme coin of the market. Those altcoins are just its subordinates and there's no other coin that be compared to bitcoin. You seem to misunderstood that bitcoin is also an altcoin, no bitcoin isn't an altcoin. It's not an altcoin whereas altcoins are copied from bitcoin which is the original and first cryptocurrency.