So what it is difference between bitcoin and other cryptocurrencies?
There are many possible differences, primarily in the protocol and consensus rules. Also, two currencies that are otherwise exactly the same will differ in their genesis block.
Bitcoin, Ethereum, and Litecoin differ many ways. There is very little chance of confusing them.
Bitcoin and Bitcoin Cash differ only in the consensus rules.
Bitcoin and Terracoin (TRC) differed only in the genesis block for a long time.