Here are a selection of sample steady state workouts (training at the same intensity). Otherwise known as base training. They're commonly referenced in periodization plans during active rest or progressive training regimes.
"Easy" steady state workouts can be great for active rest and/ or rehabiliation. Long Slow Distance (LSD) workouts are also good for distance training.
Steady-State workouts also get used for steady progression (e.g. increasing speed, duration, volume, distance etc.). You may here this referred to as "aerobic push", whereas interval training is often referenced against "aerobic pull". Steady-state workouts may also be used in conjunction with interval training (e.g. alternate days).
For further ideas on periodization, please review the many articles featured on GymProfessor.com.