The 10th day of a month (a calendar date); read as 'tooka'.
来月の１０日に会議があります。
There is a meeting on the 10th of next month.
彼の誕生日は十日なので、その日は休みを取る予定だ。
His birthday is on the 10th, so I plan to take that day off.
今月の１０日は銀行が混み合うので注意してください。
Be aware that banks get crowded on the 10th of this month.
A period of ten days (ten-day duration). Depending on context it may be read 'tooka' or 'juunichi', but here 'tooka' indicates a span of ten days.
旅行は十日間の予定です。
The trip is planned to last ten days.
その薬は十日間飲み続けてください。
Please continue taking that medicine for ten days.
申し込みから十日ほどで結果が届きます。
You will receive the result about ten days after applying.