A campanile is a bell tower built to house one or more church bells, and the term, drawn from the Italian word for bell, is used especially for towers built as freestanding structures, separate from the main body of the church rather than integrated into its facade or crossing as an attached spire or tower would be. Freestanding placement offered real practical advantages to medieval builders: a separate tower could be founded on its own solid ground independent of the main church's structure, avoided adding the bells' considerable swinging weight and vibration to walls also carrying roof and vault loads, and could be built, repaired or even rebuilt after damage without disturbing the church itself, a genuine concern given how much the sound and weight of large bells can stress a structure over time.
The most famous example, the Leaning Tower of Pisa, is in fact the campanile of Pisa Cathedral, built as a separate cylindrical tower some distance from the cathedral's own facade, illustrating clearly how independent from the main church building a campanile could be sited even for a building of major civic and religious importance.
Later builders in other regions sometimes attached a bell tower directly to the church facade or crossing rather than separating it, but the term campanile is used specifically for the type regardless of whether it stands apart from or against the church it serves, so long as its primary purpose is housing the bells rather than functioning as a spire over an occupied part of the building.