"Blender is a free and open-source 3D computer graphics software product used for creating animated films, visual effects, interactive 3D applications or video games. Blender's features include 3D modeling, UV unwrapping, texturing, rigging and skinning, fluid and smoke simulation, particle simulation, soft body simulation, animating, match moving, camera tracking, rendering, video editing and compositing. It also features a built-in game engine."

or, as I like to say, you can create mesh.
Mesh is the capability to bring 3D models, known as meshes, created in third-party tools into Second Life.
A mesh is a bunch of vertices, edges, and faces that define a 3D shape, usually made in a program external to SL (Blender), although there are in-world gadgets that allow one to convert prims to mesh (these do use an external program as part of the process as well).
It's easy to create your object, you start with a Box, then you create more faces, edges or vertices Together, they can combine to make models that look like this!

You can download Blender here and learn more with me you know where to find me or if you prefer e-mail me.