A “Modality” is a procedure where something is with the body or mind, usually intermittently for healing or maintenance. While some modalities are passive, i.e done to you (i.e. massage) others are done by you (i.e. meditation). 

There is overlap between “Therapy” and Modality, while Therapy is usually a more formal process provided or supervised by a licensed or skilled practitioner.

There is also overlap with a Protocol, which is a series of things that are done to heal or maintain.