You get one scored daily round per browser. Practice boards are random, unscored and unlimited, so you can keep playing after the daily round.
The daily round is scored once: after you finish, the day’s board stays on screen with your words and the words you missed.
Choose Practice a random board to deal a fresh 4×4 board whenever you like. Practice boards are never sent to the server, do not touch the leaderboard and do not count toward your streak.
See also How long a round is. For tips, read the Word Hunt tips and strategy.