Blender is the free open source 3D content creation suite, available for all major operating systems under the GNU General Public License.
- AE's main purpose: Video effect editing. Blender has a whole range of possibilities, but it's hard to get into and it's not designed to be used solely for video effect editing.
- Yeah, you can edit videos with it... But it's not made for it in specific and isn't it's main purpose. It has lots of purposes.
- It clearly doesn't look like after effects and has a pretty steep learning curve, but it can do anything that after effects can do.