There are so many different types of religious out there, how can I know the difference?

The Catholic Church has three types of religious institutes and societies: Religious institute, Secular institute, and Societies of apostolic life.

“A institute is every society, approved by legitimate ecclesiastical authority, the members of which tend to evangelical perfection, according to the laws proper to their society, by the profession of public vows, whether perpetual or temporary, the latter renewable after the lapse of a fixed time.” As you can see this is a very broad definition which covers all types of religious communities. The thing that all have in common is that they are recognized by ecclesiastical authority, they live a life in common in a community, they take vows, and practice poverty, chastity and obedience.

A secular institute has members who also take vows, try to perfect themselves in the evangelical councils, are also recognized by ecclesiastical authority, but they don’t live in community. (Hermits and anchorites, however, do not belong to this group but to religious institutes.)

A Society of apostolic life is one whose members live privately (no community life), nor do they take vows, but they do try to practice poverty, chastity and obedience more perfectly.

When one talks about religious and religious life you are usually referring to a religious institute.

What is the difference in these religious institutes?

Religious orders vary in 3 ways: rule, form, type, and apostolate. It is the mixture of these elements that make each order unique and give the church such diversity.