blockade

"First restrain -- then blockade -- lastly, destroy!" -- Aron NIMZOWITSCH

A blockade is just that: a block, stopping the enemy getting past a point or a line. Fischer used it as a tactical idea against Benko
Locked pawn chains are a common blockade, usually stopping both players from moving freely
If there is a blockade, then perhaps there is a fixed target you can attack.
- For example, an isolated Queen's pawn can create havoc if it is allowed to advance (Dittman-Fuchs, Kamsky-Short)

overprotection

Overprotection is an idea Nimzowitsch discussed at length, but I don't hear a lot about it these days. Nimzo thought that some important central points should be not just protected but overprotected, and this would be a good thing.
There is a concrete sense in which overprotection helps: if your weak e6 pawn is attacked three times and defended three times, you have to be careful to move the defenders only so far as they still protect e6. If you have four defenders of e6 with three attackers, you can move any defender whereever you like.

A weakness is typically a pawn that can be attacked (Chekhover-Rudakowsky) or a square that can be used (a hole or outpost) (Smyslov-Rudakowsky) [Sorry, Master Rudakowsky!]
The King's position can be weak, when an attack is more likely to succeed (Tarrasch-Mieses)
The principle of two weaknesses in the endgame says that one weakness may not be enough to lose (it gets attacked twice, you defend it twice) but two weaknesses will be much harder to manage, particularly if they are not close together (Hartmann-Yanofsky)

You can sometimes give up material and come out with an advantage.
You often see a sacrifice as part of a combination -- a sacrificial combination, in Botvinnik's language. Spielmann didn't think these were real sacrifices.
The advantage you get from sacrificing might be a mating attack (like the Greek gift) or just a very fine position where mate is still a long way off (Fried Liver Attack, Tal-Simagin, Bronstein-Rojahn). Spielmann called this last sort a real sacrifice.

Zugzwang in German means 'forced move'. It refers to a situation where you might be OK right now but if you move you lose -- and you have to lose.
Lots of endgame examples
In the Bronstein game, White will run out of pawn moves, then will have to move King or Rook -- then lose a whole Rook, and be a piece behind.

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We are often told to get at least a stake in the centre in the opening. Without this, you might get pushed off the board (Boleslavsky-Scitov, Hage-Nimzowitsch)
With less space, swap pieces if you can. You might find the home of your pawn structure now fits.

The ability to move
If your pieces lose mobility, they will find it hard to organise a defence to new threats. Pieces can lack space or just find themselves in each other's way with nothing much they can do .
Pawns can also show notable power when mobile (Korchnoi-Szabo, Bronstein-Rojahn), and appear as weak targets when they are not (Johner-Nimzowitsch).

If an enemy piece is stranded on one wing, finding it difficult or impossible to get across the board, then start a fight on the other wing. There you will be a piece ahead. (Winter-Capablanca)

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"Now I have the pawn and the compensation." --Roman Dzindzichashvili

Material refers to the pieces and pawns on the board.
Usually, if you have extra material, you have good chances to win
We have a rough rule to work out who is ahead in material: a Knight or Bishop is worth about 3 Pawns; a Rook, 5 pawns; and a Queen, 9.
- So, losing a Queen for Rook, Bishop and Pawn is actually about equal.
- Likewise, losing a Rook for Knight and two Pawns is also about equal.

A nice easy one: having more pawns than your opponent on one side (and an open file there too, otherwise we have the half-open files setting for a minority attack)
Capablanca shows Marshall that a working majority is enough to win the game: you create a passed pawn.
A working King's-side majority can produce an attack on the King (Alekhin-Marshall)
Both sides work hard to make the most of their majorities in Botvinnik-Euwe