Excel is for everyone. An employer is looking that you can create basic spreadsheets with formatting, basic formulas and functions like SUM, AVERAGE and COUNT. For the high-end skilled jobs you'll need complex function skills.
Functions are different to Formulas. Formulas use operations like + - * / where as Functions follow a structure. They both start with = A Functions has = Function Name ( in that order. There are over 300 Functions in Microsoft Excel.