What is the advantage in moving the bishop at the beginning of the game?

To be frank I suck at chess and wanted to know what the advantage was in moving the bishop so early in openings like the London defense. Is it just to threaten other pieces?

Well, in the London, white wants to play d4 and e3, but white doesn’t want to block in the dark-squared bishop. So white develops it to f4 before playing e3.

I think that’s probably the motivation behind a lot of early bishop moves — one player develops the bishop early because they don’t want it to get locked in behind another piece. Another example is in the Grünfeld: 1. d4 Nf6 2. c4 g6 3. Nc3 d5 4. exd5 Nxd5 5. e4 Nxc3 6. bxc3 Bg7 7. Bc4 c5 8. Ne2. White wanted to develop the knight to e2 (because white wants to meet …Bg4 with f3), but white didn’t want to keep the light-squared bishop locked in on f1. So white moved the light-squared bishop first.

Hope this helps!

A few more examples, but from the black side:

Caro-Kann: 1. e4 c6 2. d4 d5 3. e5 Bf5. Black will play 4… e6, but black doesn’t want to hem in the bishop — a similar idea to the London.

Owen’s Defense: 1. e4 b6 2. d4 Bb7. Black wants white to commit to either Nc3 (blocking in the c-pawn so white can’t continue to build the pawn center) or Bd3 (which is a bit awkward for white compared to Bc4).

Benoni: 1. d4 Nf6 2. c4 c5 3. d5 e6 4. Nc3 exd5 5. cxd5 e6 6. e4 a6 7. a4 Bg7 8. Nf3 Bg4. Black wants to exchange the light-squared bishop if black can, because the bishop often gets in the way in Benoni positions.

Just a few more examples demonstrating early bishop moves.

#1
The common sense principle is to develop knights before you develop bishops.
The London opening is an exception to that principle.
The principle is justified:
1) f3, c3, f6, c6 are the natural squares for the knights, where they control 2 central squares.
The optimal squares for a bishop are harder to determine and depend on pawn moves.
2) A knight on its starting square is not useful.
A bishop on its starting square is useful once a pawn has moved to open its diagonal.
The normal development sequence is: KN, KB, QN, QB
The London Opening is atypical.