What it means to play with the houses money?

Say I buy 100 shares at $1 and it goes to $2 then sell 50 shares thus taking my original investment out and keeping the other 50 shares in the market. Does that mean I won't pay extra taxes at the end of the year because I did not have a capital gain? Is that an example of how investors play with "the... show more Say I buy 100 shares at $1 and it goes to $2 then sell 50 shares thus taking my original investment out and keeping the other 50 shares in the market. Does that mean I won't pay extra taxes at the end of the year because I did not have a capital gain? Is that an example of how investors play with "the houses money"? I am confused by the term "houses money".
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