Marginal Hands?

[rocket]

What are they and how do you push them?
I'm a relatively new player, especially at big tourneys.
Most of the time with a field of 700 or so, I can crack the top 100. But, making it into the money I have not done.
From what I have read, what I believe is missing in my game is pushing marginal hands and increasing my stack when the cards are not coming my way.
Thanks in advance sharing your knowledge.