A staple in Power BI interview questions for experienced, be prepared to answer this one.   Logical Functions - These functions return information about values in the expression. E.g. AND, OR, NOT, IF, IFERROR, SWITCH etc. Math and Trig functions – These are like Excel's mathematical and trigonometric functions. E.g. SUM, SUMX, ABS, CEILING, CURRENCY, EVEN, FLOOR, INT etc. Date and time – These date and time functions are like in Microsoft Excel. E.g. CALENDAR, CALENDARAUTO, DATE, DATEDIFF ETC etc. Time-intelligence - These help in calculations on calendars and dates. E.g. SAMEPERIODLASTYEAR, TOTALMTD, TOTALQTD, TOTALYTD, DATEADD etc. Filter - These returns specific data types, related tables for looking up values, and filter by related values. E.g. CALCULATE, DISTINCT, FILTER, RELATED etc. Information - These are used on a table or column to provide as a parameter to another function and tells exits or not by using TRUE or FALSE E.g. ISERROR, CONTAINS, ISBLANK, LOOKUPVALUE etc. Parent and Child functions - These help users to manage data that is shown as a parent/child hierarchy in the data models. E.g. PATH, PATHCONTAINS, PATHITEM, PATHLENTH, PATHREVERSE. Statistical- These functions perform aggregations and can also filter a column before or create aggregations based on related tables. E.g. AVERAGE, MIN, MAX, COUNT, MEDIAN etc. Text- Can search for text within a string, or concatenate string values or return part of a string or formatting for dates, times, and numbers. E.g. CONCATENATE, FORMAT, LEFT, RIGHT, TRIM etc. Other functions – These are unique functions and cannot be defined by any above categories. E.g. ERROR, EXCEPT, GROUPBY, SUMMARIZECOLUMNS etc.