Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nf6/3. Bc4

3. Bc4
White's e4-pawn is left undefended in preference for more development.

Theory table
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'''1. e4 e5 2. Bc4 Nf6 3.Nf3''' or '''1. e4 e5 2. Nf3 Nf6 3.Bc4'''