'yd' is the short written form of 'yard' (a length of about 0.91 metres, so a little less than a metre). You see it on measuring tapes, in sports reports, on cloth in a fabric shop, and in building plans — anywhere in the United States, and in older British writing. It is written, not spoken: when you read '5 yd' out loud you say 'five yards'. Two points about the shape. First, English usually does not add -s to short forms of measurements, so '10 yd' is normal, though you will also see '10 yds' and nobody minds. Second, in modern writing the full stop is often dropped ('5 yd'), but older books write '5 yd.' — both are fine. Taiwan uses metres for almost everything, so you will meet 'yd' mainly in American sports (American football fields are measured in yards) and in imported cloth, wood, or garden materials.