What a birth chart is
It is a photograph: one moment, from one place.
A birth chart is a diagram of how the sky looked from your birthplace at the moment you were born. There is nothing mysterious in the calculation — it is astronomical data. The ephemeris tables used today are based on NASA data.
How the wheel is built
The wheel has two layers. The outer ring is the signs — the fixed division of the sky. The inner segments are the houses — drawn from your birthplace and time. The planets sit on top of both.
Reading a single placement
Reading a placement means answering three questions: which planet (what), in which sign (how), in which house (where). "Venus in Virgo, sixth house" means: the way you love is detailed and selective (Virgo), and it shows up most in daily routine and work (sixth house).
In a placement, what does the HOUSE tell you?
Planet is what, sign is how, house is where.