Here's some helpful definitions you'll come across while researching video online or on set.
All Quiet (Quiet on the Set): command for all non-story noise to stop in preparation for shooting a take.
Slate In: command for the slate to be placed in front of the camera field with the pertinent reel/shot/scene information for use in post-production.
Roll Sound/Camera: command given to the audio mixer/camera operating to begin recording.
Sound/Camera Speed: response from audio mixer/camera operator that their device is recording.
Marker: command for the slate operator to call out the scene/take and clap the slate for syncing.
Settle: command for everyone to come to a stop on set except for actors and camera relevant crew.
Action: command for the actors, camera, extras, etc. to perform the scene.
Cut: command for all action to stop and the camera and audio devices to stop recording.
Back to One: command for everyone - camera, actors, extra, audio, etc. - to go back to their starting point of the scene in preparation for another take.
Reel (Roll): indicated on the slate, it's a running tally which reel or roll of film the production is on. In digital cinema, this has come to mean which SD card or hard drive the production is on.
Dump the Card: taking the video or audio footage off the SD card it was recorded to and transferring it to a hard drive.
Pre-production: period of any film or video production before shooting begins. Scripting, budgeting, scheduling, casting, location scouting, hiring crew, set building, prop and wardrobe tests, and renting equipment are all part of pre-production.
Production: period where the bulk of shooting occurs, whether it is a one-day commercial or one-month feature film.
Post-production: period where the video and audio are put together to make a cohesive film or video. Sometimes just called 'Post'.
Pickups: additional shoots to get shots that weren't part of production or became necessary based on decisions made in post.
Spot - a commercial.
15 / 30 / 60 - short hand for commercials in their standard lengths of 15, 30, or 60 seconds.
C47 (or Bullet): a clothespin used to attach gels and diffusion material to lights. C47 became the slang term out West because on the order forms, it's catalogue number was C-47. Bullet is the more common slang for it out East because it's just how they roll.