The Target Lambda table holds the mixture you want the engine to run at each combination of load and RPM. It feeds straight into the fuel calculation, so it matters whether you're running open loop or closed loop. In closed loop, it's also the target the O2 control works toward using your wideband sensor.
The real benefit comes once the base VE table is right. From then on, the VE table describes how well the engine breathes, and the target table describes what mixture you want. The two are separate. If you want a richer mixture at full boost or a leaner cruise, change the target and the ECU recalculates the fuel. You don't have to touch the VE table again. That's why we fill the target table in properly as part of every fuel tune, rather than leaving a flat default.
The table shows values in whatever unit you've picked under Preferences > Unit Options > AFR, so you can work in lambda or gasoline AFR, whichever you prefer.
Keep targets safe: richer where cylinder pressure is high, and only go leaner at light load once the engine is stable. For more, see tuning with VE and the base fuel table.
