First, free accounts start with fewer character slots and bag slots than the paid version of the game. But they still get the full complement of slots as soon as they buy
Guild Wars 2: Heart of Thorns.
Second, free accounts have some chat restrictions and economy restrictions so that they can’t be used to disrupt the game for other players. Free accounts can use local chat and whispers, but not map chat. With whispers, they can both start new conversations and reply to existing conversations but are limited to starting new conversations no more than once every 30 seconds. Free accounts can buy and sell common goods on the trading post. They can’t mail gold or items directly to other players, trade gold for gems, or access guild vaults.
Third, free accounts have some restrictions to prevent them from skipping ahead to places where they could be used to disrupt the game. They must play to level 10 before leaving the starter zones, to level 30 before using LFG, and to level 60 before using World vs. World. They can play PvP immediately but must get to rank 20 before using custom and unranked arenas.