Wire Arc Additive Manufacturing (WAAM) is a revolutionary process under the category of Direct Energy Deposition (DED) method in the field of Additive Manufacturing (AM). The research is being done exponentially since 2011 which is integrating into the advancement of production specifically for fourth Industrial Revolution (Industry 4.0). The deposition of filler metals in layers over the substrate is done mainly through Gas Metal Arc Welding (GMAW), Gas Tungsten Arc Welding (GTAW), and Plasma Arc Welding (PAW) which are leading heat input sources to fabricate the product with improved strength of material than from other DED's. Although defects are similar as of welding defects. In this paper, concepts and processes for WAAM have been studied thoroughly and a critical review is done on important and defining parameters of good quality WAAM manufactured products. It also focuses on the recent advancements in tuning the mechanical and microstructural properties of WAAM fabricated parts and the financial aspects of WAAM for the production of cost-effective fabricated materials. Display omitted •The present work focusses on wire-arc additive manufacturing (WAAM) and highlights the key points and merits of it.•It also emphasis the developments in WAAM, especially on alloys and composite.•The effect of process parameters related to heat generation, material flow is explored.•Microstructural, mechanical characterization and defects associated with WAAM are the key highlights of the present work.