tooltip
nounUK /ˈtuːl.tɪp/
US /ˈtuːl.tɪp/
A small box that pops up to tell you what a button or picture does.
Hover your mouse over the icon to see a tooltip explaining what it does.
OTHER MEANINGS
2. A brief message that appears near an item on a screen when you point at it.
The tooltip showed the full name of the file.
3. A short note that gives extra help about a feature in a program.
Read the tooltip before you click the delete button.
4. A small label that appears above a chart point to show its value.
Each bar on the graph has a tooltip with the exact number.