map vs std price

hi gurus,

1) what is the difference for moving average price and std price? i read that map is for raw mats whereas std price for semi to finished goods.

so what actually is map and std price?

2) when there is a price difference during gr and ir, the difference will put in variance account. is it same like price difference account?

3) price difference account is p&l right? so it is expense or revenue?

4) i was told sometimes the difference can be inventorised but sometimes put in price difference account. what is the difference?

thanks