When playing match play against another golfer, you'll mark your scorecard to show how the match stands in relative terms. Think of it this way: the match starts out "all square" (tied) because neither golfer has yet won a hole. So mark your scorecard "AS" for "all square" so long as the match remains tied.
Once someone wins a hole, you'll mark the card "-1" if you lost the hole, or "+1" if you won the hole. This means you are 1-down or 1-up, respectively, in the match. Let's say you're 1-up (so your scorecard reads "+1") and you lose the next hole. Then you're back to "AS." But if you're 1-up and win the next hole, your scorecard now reads "+2" (for 2-up in the match).
If a long string of holes is halved (tied), you'll keeping writing the same thing on the scorecard for each hole. For example, you're up by one hole at No. 5. So on the scorecard you've marked Hole 5 as +1. The next five holes are halved. So holes 6 through 10 will also show +1 on your scorecard, because you remained 1-up.
The same principals apply to team match play. An example of match play with handicaps is included on the next page.