What do Odds mean say like Back 4.5 Lay 4.4? Good to get Back and Lay numbers as close as possible?
Odds are numbers that represent the chance of an outcome happening.
With matched betting you are BACKING and LAYING a selection to cover all outcomes.
Backing at 4.40 means that you are betting for the outcome to occur at the bookmaker (I.e. Team A to win, horse X to win).
Laying at 4.50 is betting against the outcome to happen at the betting exchange.
Yes, you want the back and lay odds as close as possible to maximise profit.