In one sentence, describe what the following article is about:

Solver can analyze your spreadsheet's data and any constraints you've added to show you possible solutions. This is useful if you're working with multiple variables. In order to use Solver, your spreadsheet must have data with different variables and a solution.  For example, you might create a spreadsheet documenting your various expenses over the course of a month with the output cell resulting in your money left over. You can't use solver on a spreadsheet which doesn't have solvable data (i.e., your data has to have equations). It's at the top of the Excel window. This will open the Data toolbar. You'll find this option in the far-right side of the Data toolbar. Doing so opens the Solver window. Click the cell in which you want to display your Solver solution. This will add it to the "Set Objective" box. For example, if you're creating a budget where the end goal is your monthly income, you would click the final "Income" cell. Check the "Value Of" box, then type your target value into the text box next to "Value Of".  For example, if your goal is to have $200 at the end of the month, you would type 200 into the text box. You can also check either the "Max" or "Min" box in order to prompt Solver to determine the absolute maximum or minimum value. Once you've set a goal, Solver will attempt to meet that goal by adjusting other variables in your spreadsheet. Constraints set restrictions on the values that Solver can use, which prevents Solver from accidentally nullifying one or more of your spreadsheet's values. You can add a constraint by doing the following:  Click Add  Click the cell (or select the cells) for which the constraint applies. Select a type of constraint from the middle drop-down menu. Enter the constraint's number (e.g., a maximum or minimum). Click OK Once you've added all of your constraints, click Solve at the bottom of the Solver window. This will prompt Solver to find the optimal solution for your problem. When Solver alerts you that it has an answer, you can see the answer by looking at your spreadsheet to see which values were changed. If the output that you received isn't ideal for your spreadsheet, click Cancel in the pop-up window, then adjust your objective and constraints. If you do like your Solver's results, you can apply them to your spreadsheet by checking the "Keep Solver Solution" box and then clicking OK.

Summary:
Understand Solver's use. Add your data to your spreadsheet. Click the Data tab. Click Solver. Select your target cell. Set a goal. Add constraints. Run Solver. Review the results. Change your Solver criteria.