What does it mean when the dentist is saying 3 2 3 when going over your teeth?

a dentist identifies your teeth with a number.

Sounds like probe depth readings. They take a measuring tool and feel under the gum until they get to the attachment. Normal reading should be 3mm or less. From those readings, it sounds like your periodontal readings are within the normal range. Good for you!

to expand on new shews' answer, they take 3 measurements of the gum per tooth. Essentially, they are sticking a probe between your tooth and the gum at 3 different spots to see how far down it will go.

3mm is the max depth that is considered reasonable to clean with normal hygiene. Deeper separations will allow food and bacteria to stay and erode the tooth below the gum line.