The first decision is type. An activity gym is a fabric mat with arches and hanging toys, ideal for newborns who need visual stimulation and tummy-time motivation. A foam mat is a thick, flat pad that cushions a sitting or crawling baby and protects floors. A reversible play mat is a large, printed foam sheet that doubles as a room accent. Many families own two: a gym for the first three months and a foam mat after that.
The second decision is thickness. A thin mat feels fine on carpet but hard on hardwood or tile. Look for at least half an inch of foam for floor use, and more if your baby is learning to sit and topple. Memory foam feels plush but can be heavy and slow to dry; XPE foam is lighter and wipes clean.
The third decision is cleanability. A wipe-clean surface survives spit-up, food, and diaper leaks, which is the reality of baby life. A machine-washable fabric mat is softer but needs drying time and can shrink. If you want both, look for a mat with a removable fabric cover over a wipe-clean foam core.
The fourth decision is size. A newborn fits on a small mat; a crawler does not. If you have the floor space, buy bigger than you think you need, because a mat that is too small gets abandoned and you end up buying a second one. Reversible prints let the mat face the baby for play and the room for company.
The fifth decision is safety and materials. Foam mats should be free of the chemicals you would not want a baby chewing, and seams should be tight so no small parts detach. For activity gyms, check that the arches lock securely and that hanging toys are firmly attached.