It means they’ve been verbally offered an opportunity to be on the team by the coaching staff and verbally committed to the offer. It usually involves athletic money. While both sides typically follow through nothing is official/done until a National Letter of Intent in signed senior year. An NLI is not required if there isn’t athletic money involved.
Both sides have the opportunity to walk away from the verbal offer and commit. It occurs more often in other sports than baseball. If a baseball coach changes his mind he typically tells the player, “I’ll honor my offer. But I don’t see you ever getting playing time here.” What kid follows through and accepts? Players sometimes walk away if there’s a coaching change between the offer and NLI signing day.
There are qualifications for allowing a player to receive athletic and academic money. It involves a high GPA so the athletic department can’t give academic money for athletic purposes.
When you hear about a player committing to a program it may not involve any money at all. A D1 team can only offer up to 27 players athletic money. But without athletic money an NLI isn’t signed.