I have heard the term "half positions" for a technique used in the context of barre chords.
What does it mean? What are its advantages?
Half position in reference to a barre chord using one finger to bar 2-5 notes instead of all 6 strings. There's a lot of chords that don't to be fully barred. Simple example is there is a "mini" version of the typical F chord that is:
Notice only two notes are barred so you are in half position. The distinction is made so you can tell the difference between when you need to fully barre something and when you don't. So if you were instructed to play an F chord in half positions you would play the chord above or if you were instructed to play an F chord in full position you would play the chord below:
There are times when one shape is more useful then the other so being able to distinguish each is useful.
The manner in which I used the term and it may very well be incorrect is that instead of using your Index / Middle and Ring finger to hold down the open E Major chord you do with the next set of three left hand fingers (Middle, Ring and Pinky)
This leads to having your Index finger free to bar when you go from the open E chord to any of the various E shape Barres.
Going from an open E chord with the regular left hand fingerings into E shape Barres though not impossible is a bit too advanced for people who are just starting out with trying to get the barres down.
You have to go from the regular E Maj shape break that shape get your hand into the barre shape move it to the correct position and hold the chord down. All in the space of moments a regular chord change takes. That is hard
With the half positions as I use the term your hand position stays the same from the open E chord. So you can lock your hands and just move the shape. Something which is generally easier than changing shapes while changing chords.
This also has the added benefit of training your less intelligent left hand fingers (Ring / Pinky) Which helps a lot when doing scales and trying to play lead fast.