From the main line...
If White takes this pawn, we are in the Exchange Variation...
Black has two options:
To either take take back with the e-pawn
Which is where Black plays it safely
And develops his pieces like this
To attack White’s d-pawn
Or take back with the c-pawn
Where Black plays it more ambitious
Develops his pieces like this
And counterattacks this way for White’s d4 pawn
