"In the clearing ahead, you see a pair of 9' tall humanlike figures. They seem very thin and have minor deformities- one has an obvious club foot, and the other's face looks like it's partially melted due to a malformed jaw. They wear furs and hides with pieces of metal armor stitched into strategic places, and wield spears."
View attachment 353345
From this description, how does one tell, exactly, if they are dealing with an easily dealt with threat, or a deadly encounter? You can metagame that the DM isn't going to use an encounter of two easily defeated mooks, but you really don't know. Are they as tough as giants? Trolls? Ogres? Bugbears?
No idea. Should you alpha strike by using a powerful spell, or attempt to use minimal resources? No amount of experience can let you make an informed decision, unless you know exactly what these things are from player experience.
Or again, you could metagame and think "well, this is the second encounter, we might face up to 6 more today. Or not."
Now, I could say, "this is a Verbeeg, it's slightly more dangerous than an Ogre." And maybe that's enough.
Or I could say "he has 5 hit dice, one attack, and a Strength of about 20 and a (surprisingly good, based on the description) 16 AC." Now, I know the players can make a proper tactical assessment.
D&D is a game where a little bunny rabbit can actually be a horrible abomination. Description doesn't actually tell the player very much about what they are dealing with. There are, however, cues a trained combatant can glean from someone's stance, how they carry their weapons, the condition of said weapons, and a hundred more intangibles that I don't have the time to describe (or think about in the moment).
Some feel that you should have to have a special feature, like the Battlemaster, to be able to size up foes. I'm in the opposite camp- everyone should be able to do this if they're in the business of facing down deadly foes on a daily basis.
And note, there's still lots of room for surprise, even with the information I just shared! "Hey, Fighter, did you know that when enraged, a Verbeeg Smasher can score critical hits on a 19 or 20?"
"No...I didn't."
"Now you do!" : )