Year-to-date (YTD) return measures a fund's performance from the start of the current calendar year to its latest published price. It is the most quoted number in financial news because it directly answers "how has this fund done this year?".
It is computed from the change in unit price: if a unit was SAR 10 at the end of December and is SAR 10.65 today, the YTD return is 6.5%. It is not annualized — 6.5% in June does not mean 13% by year end.
Its main limitation is that it covers a short and variable window: in February it reflects two months, in November eleven. On its own it cannot judge a fund's quality — a high-risk fund may top the YTD table in a rising year and sit at the bottom the next.
Use it as a quick pulse on the current year, and look at 3- and 5-year returns plus risk measures before forming a full picture.