I can't understand from here. Why it requires I have ethereum balance too?
You need Ethereum because you probably choose a pair of Ethereum with your token but you can pair your own token to any tokens with value.
For example:
Let’s assume your token ticker is X while you want to pair it with ETH.
You will need same amount of ETH to your own token to create ETH-X token pair.
Traders can either buy your X token with ETH or sell your X token and get ETH in return.
Is there no way just listing and sell my token only?
No, You are creating a trading pair on DEX which means you are obligated to pair your token with other token because you need to supply the initial liquidity for user to buy and sell on your pair.
You are looking for IDO or ICO if you want to sell your token without paring it to any token. You can use pinksale and other launchpad to do that.
I set my token X 100,000 and set this initial price as 1 ethereum.
And added liquidity as 1,000 token X and 0.01 eth.
Then what happen? Other trader if buy this pair, then what he get? both? Then what I get?
Still I can't understand how pair added liquidity works.
And pancakeswap asked me that how much token it can use from my token wallet.
What that means? If I set as 100,000,000 token, then pancakeswap's traders can buy that much token from me at a price I set initially?
It depends on what user will use to purchase, for example if he purchase your token using his Ethereum he will get your tokens on the starting price you set and slippage based on the liquidity and the total purchase.
You will get the trading fee on each transaction made on your token pair while the DEX bot will automatically balance both your asset based on each value. You should learn how impermanent loss since you will suffer from it in exchange from the trading fee you are earning.