I believe that is a type of Euphorbia.

Here is a link that might be useful: A similar post on Name that Plant

I always called that plant Gopher Purge. ;-)

Your plant is in the reproductive stage, meaning that it will die after it's done flowering. Remove the spent flowers (seed heads) unless you want more of this coming up everywhere in your garden.

Here is a link that might be useful: Euphorbia