When it comes right down to it, if you're adding more weight, more repetitions, or a combination of both to your chosen exercises, this is progress. If you're a novice or intermediate lifter, progress would be your ability to add at least a few pounds to all your major lifts each week. If you're a bodybuilder, being able to do 15 reps of triceps extensions when you could previously only do 12 with that same weight is progress. Cranking out an extra 10 seconds of all out effort on a sprint is also progress.
Whatever your goal is, whether it be strength, aesthetics, or endurance, you should be progressing and becoming better week after week, month after month, year after year. If you're not, it may be time to re-evaluate your workout program so that you can get back on track. If you don't know how to go about that, then having a knowledgable coach or trainer can make a huge difference. Don't get stuck in a rut. Get help. There's nothing worse than wasted time when it comes to your training.