This is the 2537th most frequent Japanese word.
土日
"土日" means "Saturday and Sunday."
Here, 土日 refers to the weekend as a whole, encompassing both Saturday and Sunday.
土日は家でゆっくり過ごします。
I relax at home on the weekend.
In this sentence, 土日 is used to ask about the entirety of the weekend, questioning a recurring pattern or event involving Saturday and Sunday.
土日も仕事がありますか?
Do you also have work on the weekend?
Here, 土日 refers specifically to the upcoming Saturday and Sunday, indicating a planned activity during these days.