In this case, Excel extracts the month from the date in cell B6 as a number, and the month in the cell C6 as a number, then tests for equivalency using the equal sign. Both dates are in January, so the formula is solved as follows and returns TRUE.
Same month as today
If you need to test a date to see if has the same month as the current date (today), you can use this formula:
Same month and year
To test that a date is the same month and year is another date, you can use this clever formula proposed by reader Eric Kalin: