Read here about physical compression, with a deep dive into the characteristics, metrics and behavior of compression in the context of tensegrity structures and concepts.
Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. The opposite of compression is tension. In simple terms, compression is a pushing force.
For a compression member, such as a column, the principal stress comes mainly from axial forces, that is forces that fall along one line, usually the centerline. The loading capacity of a short column is determined by strength limit of the material. The strength of a column of intermediate size is limited by its degree of inelasticity. A long column is constrained by the elastic limit (that is by amount of buckling).
Compression members can be straight, curved, or other shapes. See struts for a more detailed discussion. In contrast, tension members are constrained to form geodesics, or the shortest path between their origin and terminating nodes.
Compression is the action of compressing; pressing together, squeezing; forcing into a smaller compass; condensation by pressure from the Latin //com-// (together) //pressare// "to press, hold fast, cover, crowd, compress;" the Latin shares roots with Sanskrit *//prem//-/*//pres//-, meaning "to strike." 
Compression Leads To Buckling
In engineering, buckling is a failure mode characterized by a sudden failure of a structural member subjected to high compressive stress, where the actual compressive stress at the point of failure is less than the ultimate compressive stresses that the material is capable of withstanding.
The stress at which a column buckles is inversely related to the square of how slender the column is. So making a column 4x more slender makes it 16x more likely to buckle.
Buckling is explained in the video, "Lightweighting 3: Tensegrity".
Buckling 3 Strut Tensegrity
The video below shows a hammock stand buckling in real time.
Links and References
 Oxford English Dictionary, compression