A classic example for the method of images is the following, quoted from Griffiths's Introduction to Electrodynamics, page 121:
"Suppose a point charge $q$ is held a distance $d$ above an infinite grounded conducting plane. Question: What is the potential in the region above the plane?"
Griffiths continued on solving the example using the method of images setting V=0 on the plane as one of the boundary conditions saying "since the conducting plane is grounded".
Now, of course there will be an induced surface charge density. My question is, how can this be since the plane is grounded?
Does the word grounded have different meanings? sometimes it means not charged and the others it means the potential there is 0?