Defoliation/Lollipopping/LST

You defoliate to introduce more airflow and light to the plant, so if the plant is very bushy you need to remove some of the leaves, especially if they're clumped together, or the leaves that cover the sidebranches from light. Lolipopping is the same thing afaik. LST is always good when growing indoors, it results in shorter plants, but with bigger side branches. It also makes the light more evenly distributed among the branches (you want a "flat" canopy, so it's all same distance from light)