What a basement French drain does
The drain creates a path for water that would otherwise collect near the footing or enter at vulnerable joints. In many interior systems, collected water is directed toward a sump basin.
French drain vs. sump pump
A drain collects and channels water; a pump moves collected water out. That is why the two are commonly used together. Read French drain vs. sump pump for the full comparison.
Signs drainage may be part of the solution
Recurring perimeter seepage, water at the wall-floor joint, or water that returns during storms can indicate a need for better below-grade drainage. See water in the basement after rain.