Slower than you think. Genuinely — most beginners' "easy" runs are moderately hard, which is why they're always tired and never improving.
The test is simple: you should be able to hold a conversation in full sentences while running. If you're snatching words between breaths, you're not running easy, you're running hard. Easy should feel almost annoyingly gentle.
The reason this matters: easy running is where you build your aerobic base — the engine that makes everything else possible — without digging a fatigue hole. If every run is a hard run, you never recover enough to actually get fitter. Slow easy days are what let you run more.