When BTC dominance is high, it affects the alts then after BTC dips, its the alts turn to pump. Think of it as a circulation of money. This is because this is the money flow as follows:
1. Fiat (e.g. USD, EUR, GBP)
2. BTC
3. Large Cap Altcoins (e.g $ETH)
4. Mid Cap Altcoins
5. Low Cap Altcoins
6. BTC again
7. Fiat
"Altcoin" is a combination of the two words "alt" and "coin" and includes all alternatives to Bitcoin. The success of Bitcoin as the first peer-to-peer digital currency paved the way. Many altcoins are trying to target the perceived limitations of Bitcoin.The BTC pumps at once, your heart is racing. You think that the whole market goes up — because you know that the Alts are very correlated in recent months.