You have BTC and ETH.

The algorithm to generate the addresses and private keys is BIP39 with BIP44 derivation path.

The account field is used to distinguish different "bank accounts", like one for savings, one to receive donations, another for daily use, etc. These are numbered from 0.

Your used accounts:
0 - Savings
1 - ICO bridge (deposit funds to be used for ICOs)
2 - ETH Tokens

The Internal/External field (known as Change in BIP44) allows for easy selection of addresses to be used as change (pay 20$, use 25$, change 5$) targets, which as a best practice should not be the same original addresses.