Softball glove sizes range from 12 to 14 inches. Outfielders generally use sizes 12.5-13.5 inch. Pitchers and infielders usually use sizes in the 12-13 inch range.
The construction and the leather of the gloves are the same for both baseball and softball. Fastpitch gloves have smaller finger stalls and palms to provide a better fit for women and girls.
If you play both baseball and softball, it might be better to buy the larger glove.
Youth models cost about $45-50, while good adult models cost about $120-170.
Softball gloves have a bigger and deeper pocket. Various types of wrist adjustments are available to keep the gloves snug. Common is a Velcro strap that makes it very convenient to get a good fit.