What does the transfer window opening mean?
July 15 marks the first day that teams can 'officially' agree to terms over the transferring of players from one side to another. That doesn't mean that teams haven't already made deals and players haven't already moved. Their deals are just official worldwide come July 15.
Every player in the world is essentially available, although each team has its own list of which players actually are, in reality. Last year the Union acquired central defender Juan Diego Gonzalez during the window, back on August 5, 2010.
Another transfer window occurs in January, but not nearly as many transfers happen during that month because half a season is gone in a typical soccer league, which means that prices are usually inflated by a significant margin versus a summer transfer.
Teams around the world spend regular money on transfers, how does it work in MLS?
Essentially, allocation money is just cash. However, because MLS is single-entity and controls almost every aspect of player movement into, and out of, the league, the allocation cash isn't equal to normal, papery monetary notations.
No one outside of the league or its teams knows exactly how much money each team has in allocation money. No one knows how much is spent on players coming in. That's how MLS plays the game.
Other than the allocation money isn't actual money situation, transfer work exactly the same. Players are bought and come to the league, just like any other place.
Why is it called a transfer instead of a trade?
A player moves to another team in a transfer, but it's not just simply that and it's done. A transfer involves a player's team agreeing to a transfer fee, which then gives the buying team the right to negotiate a contract with the player.
Basically, a team pays money to rip up a player's contract. The rights of the player, that is the rights to negotiate personal terms, are being transfer - not the actual player (yet).
How many roster spots do the Union have left open?
The Union currently have only 24 players on roster after the Jordan Harvey trade, giving them use of up to another six roster spots.