what is Enlist=false means in connection string for sql server?

I am a beginner with .net. I faced issue with the following error

"The transaction operation cannot be performed because there are pending requests working on this transaction.".

i read somewhere in the blog .i appended my connection string with enlist=true and the issue was resolved.

Note: i am upgrading my DB from sql server 2005 to sql server 2008R2.

Please help to understand the importance of using enlist.