1e5 is a shortcut for 10,000 which is 1 with 5 zeroes.

Think of a token as a cake made of 10,000 pieces. The token is still 10,000 while each piece can be 20 or 1, the equivalent to 0.0002 and 0.00001.

The decimals determine how small you can slice your token cake. A token is still 1 but we have to represent it in the smallest unit. We have to write all the pieces that’s why I said 1e5 instead of 1.

Put it simply, if 1 full token = 1 piece, then we can’t slice it, we can’t have decimals so you must buy the entire piece everytime. Can you imagine having to buy an entire bitcoin everytime you want to particpate in this cryptocurrency instead of buying fractions?

So if 1 full token = 10,000 pieces, then we can slice it and we can buy 0.002 pieces of token. Hope that’s clear, let me know if there’s confusion in that regard.

The confusion comes from the fact that we can’t have decimals in solidity and we must write everything as a full number to represent tokens with all of their decimals.