This Latin maxim has evolved considerably since its inception in Roman law, where it's application was mostly to determine that trees and crops were sold with, and formed part of the land.
It now translates to "whatever is affixed to the ground, belongs to the ground" and is the basic law of fixtures.
Thus, following quicquid plantatur solo, solo cedit, loose bricks are chattels; moveables or personal property and do not form part of the land, no mattter how high a pile of them. However, once cemented together and used to erect a house, the bricks become part of the land and thus converts from chattel to real property.
In residential tenancy law, the maxim is of great import as any improvement made by a tenant which attaches and converts, by srtict operation of quicquid plantatur solo, solo cedit, to real property, becomes part of the landlord's property and cannot be severed or reclaimed by the tenant at the end of the lease.
To distinguish the strict operation of the quicquid plantatur solo, solo cedit rule in certain cases, such as in mortgages (between mortgagees and mortgagors), and tenants and landlords, the law has developed a companion doctrine of fixtures. Chattels which convert to real property by operation of quicquid plantatur solo, solo cedit are called fixtures.