Load Check for Dummies

I see people ask for these quite often.
Can someone in the know tell me:
Where do you get them from?
How do you decipher them (I have a rough idea, I know the fare buckets, but unsure what the numbers infer exactly)?
Are they accurate?
I could not find a clear answer online.
Can someone in the know tell me:
Where do you get them from?
How do you decipher them (I have a rough idea, I know the fare buckets, but unsure what the numbers infer exactly)?
Are they accurate?
I could not find a clear answer online.