Various religions orders have 3rd orders, as the Discalced Carmelites.
My wife and myself are 3rd order Discalced Carmelites, OCDS. We are now inactive, as we’re no longer part of a community.
OCDS is a third order, but the term “Secular,” was added to distinguish between lay people who are third order members, and religious who are also 3rd order members.
St Pope John Paul II, was a 3rd Order Discalced Carmelite.
Third orders are for those who desire to follow the spirituality of the order, while remaining in their state of life.
So, as a married couple, my wife and myself wanted to follow the contemplative spirituality of the Discalced Carmelites, so we became Discalced Carmelites.
Third order members generally make promises, as do Discalced Carmelites. However, third Oder Discalced Carmelites have the option of making vows the year after making their definitive promises. My understanding is that the Discalced Carmelites are the only order which allows 3rd order members to make vows.
Third orders have a asperiancy and formation periods, which a person seeks to become a member and part of a community.
For OCDS members, it takes about five years.
Other orders such as the Franciscans, it may vary.
Oblates are those who are attached to a Benedictine Monastery. I’m not familiar on Oblates other than they follow the Rule of St Benedict for lay people.
In all, if you have a group near you, seek them out and visit. They’ll be more than willing to introduce you to the group.
Jim