When it comes to memecoins, it needs to be mentioned: Most "Memecoins" are not even coins, most "Memecoins" are tokens.
Often, it is just a marketing move to designate a crypto asset as "Coin" but in reality, it's a token.
A coin is based on its own, unique Blockchain, like Bitcoin, Litecoin or Dogecoin
A token is based on an existing Blockchain, like Ethereum tokens (for most ICOs) or based on BNB (for many Memecoins).
And today, most "Memecoins" are not even coins, most "Memecoins" are tokens. Keep in mind when investing.
A coin based on a side chain is generally called a token but there's no rule that prevents us from calling it coins. There are less and less coins with their own blockchain and still we call all of them cryptocoin. It's good to know what has its own blockchain and what not but technicality of strictly using the term coin and token are not worth it.
Ethereum first introduced the token system in blockchain but they used the term sub-currencies for coins that are generated using its token system.