Sam has the ability to project his bio-energy as an extra-dimensional field capable of absorbing, analyzing (causing a complete subconscious understanding) and replicating any form of matter or energy. This field is most commonly used as a protective filter. Since the field is an extension of his body's own energy he has complete control over it's shape, most commonly forming it into spheres, cubes, flat planes and for just himself he likes to form it into a tightly fitting field around himself and anything in contact with him. As touched on earlier, he has the ability to replicate anything he has already encountered within one of his fields, thus allowing him to create a normal air atmosphere when traveling in harsh environments such as underwater, the vacuum of space, or areas with high levels of radiation. The absorption and replication properties of the field also allow him to use them as short range teleportation by moving in and out of them or sending objects through it and having the field materialize the object elsewhere.
(Note: with careful study and practice, certain ways his abilities are used could be considered similar to and have many of the same end results as FMA's alchemy.)