There are several ways that captioning can be used in a church context.
Realtime captioning - done live, either remotely or in-house, and displayed with video (typically a TV, but any monitor or screen could be used).
Offline captioning - done in a post-production environment for videos & DVDs.
LED panels - another method for displaying captioned text in a live setting, without a video component.
Subtites and Webcaptions - done with special software that enables video and live video to be seen and heard by a much larger audience.
Captioning vs. Sign Language - both methods are very effective. Sign language is a powerful voice among those who live in the Deaf culture. For people who don't know sign language, captioning allows them to read what is being said and to be included.