The Kryptonian Warsuit was created late in Krypton's historical development. It was used in situations due to the protection and increased strength that it provided the user. These included construction, protection from harsh environments and warfare.
Superman received a battlesuit when it was created by his Kryptonian service robots using blueprints from the saved Kryptonian wreckage. This was done while he expanding his Fortress of Solitude and learning more about his Kryptonian heritage in the late 80's. It was mostly seen and used in the late 80's to early 90's, but has been seen a few time in Superman's recent history, but sometimes with an updated look.
It has been used mostly by Superman either wearing it or remote controlling it, but it has also been worn by Emile Brown with permission and Lex Luthor after he stole it, later using it to sustain his dying clone body.
The elements of the armor were reverse-engineered and used to create the Simm-Bot battle armor used by the Metropolis Special Crimes Unit.