How to count development
Development
What is development?
When a peice that could not previously move is made to be able to move.
Why is it good?
Power in chess is measured in maneuverability and choice, more development means more power.
What if you are black?
You will be behind in development, your goal is to castle as quickly as possible to reduce the pressure of white who is ahead in development.
How to count development
How do we count the development? Is white 1 and black 0 (White is ahead 1 tempo in development)? Do we count the bishops as well (White would still be ahead 1 tempo in development)? Do we average it out and say that when black moves, we'll be 0 tempo ahead, right now we are 1 tempo ahead, so in truth we're only 1/2 a tempo ahead? It's largely a matter of preference. You can also count pawns as a tempo of development, especially in the early-mid game. You can also sometimes count unmoved rooks and queens developed when they are on open files. You could also count knights further up the board as 'extra' developed.
As black (as a defender), you can count tempo as how many moves it will take for your rooks to see one another.
What do we do with development?
We can put increasing pressure on a piece by stacking a bunch of attacks on top of it. They will not have the defensive power to match your attacking power.
A lead in development can be converted into anything. E.g. An open file for a rook. You could acheive your positional plan. You could create space, cause a bind, create weaknesses, open up a diagonal.