Beginner roller skating
The Plow Stop: The Easiest Stop to Learn

Feet wider than your hips, push your heels apart, toes slightly in, knees bent. Both feet stay down - no single-leg balance needed. The most useful stop long term.
The plow is the first stop to learn because it works on quads and inlines, needs no special hardware, and keeps both feet on the ground.
Roll with feet a little wider than your hips. Push your heels apart so the toes turn in, then press down and outward through the whole foot. The friction does the work — do not try to force the skates together.
Learn it at walking pace on a flat surface first. Speed makes it easier, not harder, but only once the shape is automatic.
Keep going: this is one section of the full Roller Skating for Beginners guide — sizing, gear, stopping, and where to skate, in one page.