1. What's the difference in between a maker and a taker? 

When you place an order that is immediately filled (like market order) you are a taker and you pay taker fee. Basically, you are taking orders that are already on the market waiting to be matched (like limit orders).

Meanwhile, when you place an order that doesn’t fill immediately (like a limit order), you are a maker. You make the market for takers. Usually, a maker fee is lower than taker fee. Note: if a limit order that gets executed immediately (its limit price matches market price) it will be charged with taker fee.

Matching engine will always benefit the price for a taker. Meaning the taker might get a better deal than the one expects while a maker will always get only what's expected if an order gets matched.

Eg: Maker's order "SELL BTC 1 @ BTC/EUR 3,000 " will be matched with taker's order "BUY BTC 1 @ BTC/EUR 4,500 " at maker's price - BTC/EUR 3,000.

2. Supported decimals. 

BITNORDEX only supports a correspondingly specified amount of decimals. In case you deposit an asset containing more decimals, those will be floored and will no longer belong to you, so, please, be advised not to deposit amounts of more decimals than specified here. Also, BITNORDEX would like to stress that we will never support more, than 8 decimals.
Eg.: ETH originally contains 18 decimals, but BITNORDEX supports only 8. In case of a deposit of ETH 3.0000'0008'9999'9999'99 it will be floored to ETH 3.0000'0008 (this amount will be credited to your BITNORDEX balance) and you'd loose ETH 0.0000'0000'9999'9999'99.

3. Self-trade prevention

BITNORDEX does not validate/open self-trade orders. If such order conflict occurs, you will be alerted with a corresponding alert: "Order failed: self-trade".
Eg.: If you have an order to BUY BTC 1.0000'0000 @ 3,500.00 BTC/EUR, BITNORDEX will not validate/open any matching counter order from you @ a price rate of <=3,500.00 BTC/EUR, like SELL BTC 2.0000'0000 @ 3,499.00 BTC/EUR.