Photoshop Guide (?) Lines

[PSUser]

Yesterday I went to an interview for a job at a design company, and while working on an exercise in Photoshop, discovered that there is a very handy feature I had not known about.

While I was moving images around in Photoshop (on the same canvas) these helpful lines would appear from time to time to show me when an image was aligned with another, or when an image was centered etc..

Anyone know what this feature is called? I forgot to ask about it during the interview.

Thank you.

[parabola]

smart guides