Difference between account key and accrual key & their use

Hi Experts,

In pricing procedure what is the difference between account key and accrual key.

Also please clarify the when to use account key & when to use accrual key?

How account determination works.

For GR & invoice, which key will make what entry (Debit or Credit) to the G/L account assigned to it.

Is accrual key works similar as WRX key??

please clarify......

Thanks & Regards