Review articles are a good way to familiarize yourself with trends and key ideas in current Engineering journals. These are usually annual or monthly cumulations of articles or citations to articles that give you a brief summary of research and findings.
A preprint is a full draft of a scholarly article before it has undergone formal peer review and publication in a journal. It is an early version of a work that researchers make available to the scientific community.
Preprints are publicly available to anyone and allow for early dicussion on current research findings.