No, it's not an altcoin in the least. The lighting-network is an off chain protocol which is one of the many proposed ideas in order to help fix the scaling issue which we all know that Bitcoin is facing, this even relies on SegWit in order to function so that's something that has to be done before LN.
Even BlockStream (a company which is compromised of most of the people from the bitcoin core team) is supporting LN -- check all of this here https://en.wikipedia.org/wiki/Lightning_Network
That's right, the Blockstream token system is the essentially altcoin system (are they still even working on this? I think Ethereum came around and did this and took away the need) The LN network opens channels that allow essentially unlimited transactions without needing to pay fees for the transactions and require just a single fee when the channel is closed.Even BlockStream (a company which is compromised of most of the people from the bitcoin core team) is supporting LN -- check all of this here https://en.wikipedia.org/wiki/Lightning_Network
So you take a huge majority of transactions that recurring and make them channels (exchanges) you make them channels, this allows back and forth coin without large fees and wait times.
This lowers the txs per block and with segwit truly helps solve the bloated block issue.
