I wish THEY wouldn't explain it; it makes donks play better.
Basically, what they're talking about is pot odds
. When you call a bet you need to have the expectation that you'll win more money from the pot than you're putting in, so for instance if your money accounts for 1/3 of the pot total after you call you need to win the whole pot over 1/3 of the time (that is to say more than 1 time for every 2 you lose), so your odds are 2:1.
Keep in mind though, that to be profitable you have to keep within your odds AT ALL TIMES, and if you make a call with incorrect odds and then later in the hand call with correct odds you're just reducing your previous mistake not eliminating it -- you'll fundamentally still lose money from the play. A good rule of thumb is that you should only play a hand from the beginning with the expectation that you will win more money than you put in from the get-go, which is why playing tight is nearly always best.