Base currency is the currency you want to buy or sell. All quantities (in orders and trades) are measured in units of base currency. For example, sending an order with quantity 1 for instrument BTC/USDT means that you want to buy or sell one Bitcoin (BTC).
Quote currency is the currency in which you pay for buying base currency or which you receive for selling base currency. All prices (limit orders, trades and so on) are defined in units of quote currency for one unit of base currency. For example, price 6723.2 of the instrument BTC/USDT means 6723.2 USDT per 1 BTC.
Price step defines minimal price change when placing an order. For example, you can send orders with prices 6524.4 USDT per BTC and 6524.5 USDT per BTC, but not 6524.35. The general rule for selecting the price step is that the total number of meaning digits must be around 5. That's why BTC/USDT has 1 decimal point (6524.5) and ETH/USDT has 2 decimal points (202.18).
Minimal volume and volume step define the quantity of base currency you can trade on the exchange. For instance, the minimal order size for BTC/USDT that clients can send is 0.001 BTC, the next is 0.0011 BTC, 0.0012 BTC and so on.
Maximal distance shows how far from the mid price (mid between the current best bid and the current best offer) new limit orders can be placed. Restricting the range doesn't allow to show fake manipulative intentions and increases the overall stability of the market.