The French Defense: A Beginner's Guide

Introduction

https://lichess.org/study/GhYeTWlS Full study for your reference. Please refer to this along with the text here.
https://lichess.org/study/GhYeTWlS/Kzgs6CGz
https://lichess.org/study/GhYeTWlS/tcNj00L6
https://lichess.org/study/GhYeTWlS/4SlThpq4
https://lichess.org/study/GhYeTWlS/B0fKrGHR

The French Defense is one of the most common responses to 1. e4. Among top grandmasters it is the third most common reply, after 1...c5 and 1...e5. The characteristic move of the French --- 1...e6 --- helps to control the important d5 square and assists a central strike with 2...d5 next.

A disadvantage early on is that oftentimes the light-squared bishop on c8 loses scope and feels trapped there. As a result one of black's main goals is to trade this bishop for a bishop or even a knight, or even better, try to get it along the a6-f1 diagonal, where it can be a monster attacker.

Oftentimes white will play 2. d4. As I mentioned in my 'What to do in the opening' blog, having two pawns in the center is always a plus. Here black will back up his first move and strike immediately in the center with 2...d5. Here white has four common replies, and we will examine each of them. They are 3. exd5, 3. e5, 3. Nc3 and 3. Nd2.

Exchange Variation

The first line we will take a look at is if white plays 3. exd5, known as the exchange variation. This is the easiest line for black to play, and more than 50% of the games in this line end in a draw.
Black will respond with 3...exd5 (naturally), keeping a pawn in the center. There are two ways to play this, but for starters I would suggest the following.

To whatever move white plays you will respond with Nf6. Whether it be Nf3, Bd3, or c4, the top 3 moves in this position. In order to lead to equality you can even copy white's moves if they are sensible. A sample line is included in the study linked. After 11...Rfe8 the evaluation is +0.2 and out of the hundred some odd master games virtually every game ends in a draw. This is the easiest way to play for black to ensure equality, which after all isn't bad considering you are a tempo down.

You can also play aggressively in an exchange French by castling queenside and starting a kingside attack.

Advance Variation

This is a little trickier to play for black, but the advantage is that black's ideas here are going to be crystal clear. After 3. e5 white is taking space on the kingside and hopes to restrict the kingside knight. If ever your opponent extends and tries to gain space like this you must immediately strike in the center. And so I am going to recommend the move 3...c5!

From this point on the d4 pawn is a permanent target. We are going to bring all of our pieces to that square and pile up pressure. In the study I have made annotations to show sample plans for white.
The best move for white is to play c3, keeping the center intact. If any other move is played black will be happy after cxd4 and putting pressure on the isolated weakness on e5.
After 4. c3, Black will continue his plan with Nc6, mounting the pressure, and after Nf3 black will play Qb6, putting maximum pressure on that one d4 pawn.

Here white has 3 main moves: 6. Be2, 6. Bd3, and 6. a3. a3 is the most common move, hence we will analyse it first.

6. a3

This move is the most popular move among top level games. The idea is to play b4 and undermine the c5 pawn. However, there is a very simple way of stopping b4, and that is 6...c4! After white tries to play b4 by Nd2, adding protection to the b3 square, we simply control it by Na5.
Black's play will revolve around the queenside, as indicated by the arrows, while also trying to stop White's kingside attack with f4 and f5. Black will castle queenside as that is the main plan here.

6. Be2

The 2nd most popular move after a3, and a very solid one. As black you will exchange on d4 and play Nge7, planning to play Nf5. You can take a look at the study line for that.

6. Bd3

This is the Milner-Barry Gambit. White is setting a trap which you must be aware of. I have covered this in the study, but you should take on d4 once and then play Bd7. If you take with the knight again you will lose your queen to a discovered check. See the study for a sample line.

Classical/Tarrasch Variation

I'm combining these two together because we are going to play the Rubinstein variation. This way, you will only have to memorise one line for both variations so you are saving yourself some theory memorisation. After 3. Nc3/3. Nd2 you will play dxe4 and after 4. Nxe4 you will get the same position regardless of the variation. We will play the Blackburne defense with Nd7, hoping to play Ngf6 and if Nxf6 recapture with our knight. After white plays Nf3 and we execute the plan mentioned we get this position, rich in ideas for us:

As indicated by the arrows, black has a solid game after Be7 and castling and striking with c5. We can also utilise the long diagonal for the light squared bishop via d7-c6, turning supposedly the worst French piece into a monster bishop on that diagonal. I've played a sample line in the study, and you can see that Black is doing just fine.

Conclusion

This is just an intro to the French Defense. I hope after seeing these lines you will be inspired to try it one time, and I promise you that you will get a great middlegame position to play. Good luck!