Depending on how long you've been training, you may have forgotten where you started or how you got to where you are today. Now you're tossin' weight around like it ain't no thang. It may have slipped your mind that you likely started with body weight or relatively light weights.
On the other hand, maybe you've started training, but you're not sure how to get better and stronger, aside from adding more weight to your lifts.
Progressing an exercise can be done in a plethora of ways. You can add more weight, increase reps, increase sets, increase time under tension, manipulate rest times, improve form, increase range of motion, and switch modalities.
So, what does it look like to increase your range of motion or switch modalities?
Range of Motion (ROM)
Your range of motion will be affected by gains in your strength and mobility. One isn't more important than the other; they both need attention.
Let's take a squat for example. If you have a hard time lowering into a squat at or below parallel, it could be due to tightness in at least one area. But, as you may or may not know, tightness does not equal strong. In fact, it can often mean weak. Wah wah. So, let's say you continue to squat above parallel without addressing range of motion. This is totally fine! Not everyone has hopes and dreams to go ATG (ass to grass) in a squat, but for those of you that want to use and improve your ROM, working in your end ranges is important.
In reference to squatting, you could potentially improve your ROM by working on opening up your hips, strengthening your glute muscles, and/or addressing your ankle mobility. You could also incorporate things like box squats, elevated heel squats, or pause squats to increase your strength at end range positions.
*Please be evaluated by a qualified professional before jumping into any or all of these suggestions.
Modalities
On a less complex scale, switching modalities can offer new challenges. Going off of the squat example, you could progress by starting with a body weight squat, adding a resistance band, switching to a dumbbell or kettlebell, then switching to barbell. There are other types of squats you could add in or swap out for such as a hack squat or landmine squat.
I won't bore you with going over every squat under the sun, as we'd then be here for days, but following a simplified progression of modalities could look like:
Body Weight - Resistance Band - Dumbbell/Kettlebell - Barbell
Working with a trainer is beneficial to understand how you could and are progressing in your training. Always ask questions!