"Help" means helping a teammate accumulate free lives. You can help every player once for every life request. When a player gets the 5 lives they requested, the asking lives bar disappears from the chat.
In the “My Team” section, you can see how many times a player on your team has helped other teammates.
On the Team Info pop-up, it shows the weekly helps of a team. This shows how many times free lives were sent in that team during the week.
Helps are reset every Sunday night.