The spread is the distance between the bid and the ask. If you buy at the ask and the price does not move, closing at the bid realises a loss equal to the spread. That is a real cost, paid on the way in.
Some accounts advertise a raw or zero spread and then charge a commission per side, often per lot. A 0.0 spread with 3.50 dollars a side is 7 dollars round turn before any slippage. On EUR/USD, where a pip is about 10 dollars a standard lot, that commission is roughly 0.7 of a pip. A ‘no commission’ account showing a 1.2 pip spread can be more expensive, or less, depending on the moment.
Average spread, minimum advertised spread and the spread right now are three different numbers. Market Explain will not print a live spread until a feed arrives with a timestamp and a named source. An advertisement that says ‘from 0.0’ is stored as an advertisement, not as a measurement.
Swaps, or overnight financing, sit on top. A trade held past the roll can pay or receive a credit. Swap-free accounts often replace that with an administration fee. The name on the account does not remove the cost.