Hi, the full sentence is " I am all talk and no action" It refers to people who say they are going to do something but never do it. Example: That guy is all talk and no action. For 5 years, he's been saying that he's going to improve our work conditions and nothing's happened so far.

talks about doing big, important things, but doesn't take any action. other similar idiom He is all talk and no trousers http://www.usingenglish.com/reference/idioms/all+talk+and+no+trousers.html

all talk, no action

it's means that only talk and not to act