Fusion 360 and AutoCAD LT are both CAD applications. Fusion 360 is a 3D modelling and manufacturing cloud software, whereas AutoCAD LT is a 2D drafting software that can be used to draw 3D objects manually. AutoCAD LT integrates with industry-specific tools such as AutoCAD Architectural, Electrical and Mechanical whereas Fusion 360 focuses on industrial design (mechanical engineering).
AutoCAD LT is primarily a drafting package that creates a machine, house plans, schematics and plant layouts. Updates of related 2D and 3D models must be done manually. Fusion 360 is primarily an engineering package that simulates how the machine moves, assemblies of parts, mechanics, finite element analysis, complex surfacing, rendering, detailed 2D drawings based on 3D models or assemblies that are updated whenever the 3D model changes.