Pot Up To Keep Roots Healthy and Happy
Potting-up is when you take a plant that's in a small container and transplant it to a larger container so the roots have plenty of room to grow nice and healthy. If the roots have nowhere to go, they'll become tangled and bound-up. This can cause major problems when your plant is trying to uptake nutrients.
Some plants grow very well in a small container and can continue for their entire life in that environment, but most plants prefer being potted up into a bigger container so their roots have plenty of space to grow and thrive.