It is a term to identify the next batter in the line up after the current batter.
On-Deck
The next batter that is waiting to bat is referred to as being on deck.
The On Deck circle, because its where the batter that is on deck stands
it means that you are up next to bat like if your coach said "Sam is up Taylor's on deck
They are the same thing!! "Why softball is better than softball?"
They named it softball because the game of softball was derived from Baseball. The baseball had a hard core whereas the softball has a soft core, so they named it softball. Although the ball is not softball the core of the ball is soft.
A question about softball.
softball
To play softball
A softball
a softball
softball