Pricing plans and indicator
Altcoin is any crypto asset different than Bitcoin.
Also called with affection "shitcoin", they're characterized by how useless they are in the real world (for now).
Altcoins are following Bitcoin. Bitcoin is the crypto indices like the DOW JONES is the indices for US stocks.
Obviously talking of ALTs expressed against fiat or stablecoins.
My strategy with alts is not trading them and focusing on Bitcoin most of the times I'm trading crypto. For ALTS, taking the positions whenever there is a high volatility.