With Excel on a Mac a line break is entered by adding the Command (cmd) key to the other two - cmd alt enter. The Command key may be replaced by the Control key (ctrl) in some versions of Excel - It's a Microsoft thing.
Alt + Enter
It gives you a line-break inside of a cell.
Alt+Enter
A broken line. - - - - -
Shift + Enter
Press the ENTER key one for a line break and twice to enter a blank line between text.
enter
dotted red line
shift +enter
To insert a line break in HTML, use the <br> tag where you want the break to occur. In Markdown, you can create a line break by ending a line with two spaces and hitting enter. In programming languages like Python, you can use \n within a string to indicate a line break. For word processing applications, pressing "Enter" typically creates a new line.
In Word, yes. In Excel, no.
Recommend the free on-line courses offered by Microsoft. You can learn everything from How to Enter Formulas to Creating Charts. See the related links for training for Excel 2003 and Excel 2007.